<PAGE>   1
                                                                    EXHIBIT 10.6


                                  OFFICE LEASE


                                     BETWEEN


                     BOSTON PROPERTIES LIMITED PARTNERSHIP,



                                  (AS LANDLORD)


                                       AND


                               OTG SOFTWARE, INC,


                                   (AS TENANT)





                           THE PRESERVE AT TOWER OAKS
                            2600 TOWER OAKS BOULEVARD
                               ROCKVILLE, MARYLAND

<PAGE>   2


                                TABLE OF CONTENTS


<TABLE>
<S>                                                                           <C>
ARTICLE I         THE PREMISES                                                 1
ARTICLE II        TERM                                                         2
ARTICLE III       BASE RENT                                                    6
ARTICLE IV        ADDITIONAL RENT                                              8
ARTICLE V         SECURITY DEPOSIT                                            20
ARTICLE VI        USE OF PREMISES                                             23
ARTICLE VII       ASSIGNMENT AND SUBLETTING                                   26
ARTICLE VIII      TENANT'S MAINTENANCE AND REPAIRS                            31
ARTICLE IX        TENANT ALTERATIONS                                          33
ARTICLE X         SIGNS AND FURNISHINGS                                       35
ARTICLE XI        TENANT'S EQUIPMENT                                          38
ARTICLE XII       INSPECTION BY LANDLORD                                      41
ARTICLE XIII      INSURANCE                                                   41
ARTICLE XIV       SERVICES AND UTILITIES                                      43
ARTICLE XV        LIABILITY OF LANDLORD                                       46
ARTICLE XVI       RULES AND REGULATIONS                                       48
ARTICLE XVII      DAMAGE OR DESTRUCTION                                       49
ARTICLE XVIII     CONDEMNATION                                                51
ARTICLE XIX       DEFAULT BY TENANT                                           52
ARTICLE XX        BANKRUPTCY                                                  57
ARTICLE XXI       SUBORDINATION                                               58
ARTICLE XXII      HOLDING OVER                                                60
ARTICLE XXIII     COVENANTS OF LANDLORD                                       61
ARTICLE XXIV      PARKING                                                     62
ARTICLE XXV       GENERAL PROVISIONS                                          64
ARTICLE XXVI      ROOFTOP COMMUNICATIONS                                      68
ARTICLE XXVII     RIGHT OF FIRST OFFER                                        72
</TABLE>


RIDER NO. 1 -- Renewal Term
EXHIBIT A   -- Diagram of Premises
EXHIBIT B   -- Work Agreement
EXHIBIT C   -- Rules and Regulations
EXHIBIT D   -- Form of Declaration of Lease Commencement
EXHIBIT E   -- Janitorial Specifications
EXHIBIT F   -- Form of Non-Disturbance, Attornment, Estoppel and Subordination
               Agreement
EXHIBIT G   -- Form of Sublease
EXHIBIT H   -- Diagram of Reserved Parking Spaces


                                       i


<PAGE>   3

                                  OFFICE LEASE

                                   TOWER OAKS


     THIS OFFICE LEASE (this "LEASE") is made as of the 27 day of June 2000 (the
"EFFECTIVE DATE"), by and between BOSTON PROPERTIES LIMITED PARTNERSHIP, a
Delaware limited partnership (hereinafter referred to as "LANDLORD") and OTG
SOFTWARE, INC., a Delaware corporation (hereinafter referred to as "TENANT").

                                    RECITALS:

     A. Landlord is the developer and owner of a seven (7) story office building
known as "The Preserve at Tower Oaks", located at 2600 Tower Oaks Boulevard,
Rockville, Maryland, situated (or to be situated) on certain real property owned
by Landlord (all such real property is referred to herein as the "LAND"). Said
office building consists of seven (7) stories totaling approximately one hundred
eighty-nine thousand nine hundred forty-eight (189,948) gross square feet of
above-grade office space, a three (3) story parking deck, a surface parking lot
and other related improvements. Said office building is referred to herein
interchangeably as "THE PRESERVE AT TOWER OAKS" or the "BUILDING." The Building
may become part of a multi-building Complex (the "COMPLEX").

     B. Tenant desires to lease space in the Building from Landlord, and
Landlord is willing to rent space in the Building to Tenant, upon the terms,
conditions, covenants and agreements set forth herein.

NOW, THEREFORE, the parties hereto, intending legally to be bound, hereby
covenant and agree as set forth below:

                                   ARTICLE I
                                  THE PREMISES

     1.1 Landlord hereby leases to Tenant and Tenant hereby leases from
Landlord, for the term and upon the terms, conditions, covenants and agreements
herein provided, approximately 93,735 square feet of rentable area, comprising a
portion of the first (1st) floor and the entire third (3rd), fourth (4th) and
fifth (5th) floors of the Building (the "PREMISES"). The location and
configuration of the Premises are outlined on Exhibit A attached hereto and made
a part hereof.

     1.2 The lease of the Premises includes the right, together with other
tenants of the Building and members of the public, to use the common and public
areas within the Building, but includes no other rights not specifically set
forth herein. The lease of the Premises also is subject to any covenants,
conditions and restrictions of record, including but not limited to that certain
Declaration of Covenants dated February 6, 1996 recorded in Deed Book 139333 at
Page 448, among the land records of Montgomery County, Maryland, as amended by
that certain Agreement of Modification of Tower Oaks Property Owners
Association, Inc. Declaration of Covenants, Conditions, Easements and
Restrictions dated May 27, 1998, recorded in Deed Book


                                       1
<PAGE>   4

15897 at Page 112, among the land records of Montgomery County, Maryland
(collectively, the "Declaration of Covenants"), a copy of each of which has been
delivered to Tenant prior to the date hereof. Tenant agrees to observe and
comply with all provisions of said Declaration of Covenants which may be
applicable to it.

     1.3 Landlord shall engage Gensler to determine the exact number of square
feet of rentable area included in the Building and the Premises. Promptly after
Gensler determines the exact number of square feet of rentable area in the
Building and the Premises Landlord and Tenant shall execute an amendment to this
Lease stating, among other things, (a) the exact number of square feet of
rentable area (as determined in accordance with the Standard Method for
Measuring Floor Area in Office Buildings established by the Building Owners and
Managers Association (1996)) included in the Premises and (b) Tenant's
proportionate share as determined in accordance with the provisions of Section
4.1(a) below, which amendment shall be in the form of the declaration attached
as Exhibit D hereto.

                                   ARTICLE II
                                      TERM

     2.1 All of the provisions of this Lease shall be in full force and effect
from and after the Effective Date. The term of this Lease (hereinafter referred
to as the "LEASE TERM") shall be for one hundred twenty (120) full calendar
months, commencing on the Lease Commencement Date, as determined pursuant to
Section 2.2 hereof, and continuing for a period of one hundred twenty (120) full
calendar months thereafter, unless such Lease Term shall be terminated earlier
in accordance with the provisions hereof or extended pursuant to Rider No. 1 to
this Lease. Notwithstanding the foregoing, if the Lease Commencement Date shall
occur on a day other than the first day of a month, the Lease Term shall
commence on such date and continue for the balance of such month and for a
period of one hundred twenty (120) full calendar months thereafter. The term
"Lease Term" shall include any and all renewals and extensions of the term of
the Lease.

     2.2 The Lease Commencement Date shall be the date that is the earlier to
occur of (i) the date on which Landlord substantially completes (or is deemed to
have substantially completed) the Leasehold Work in accordance with the
provisions of Exhibit B, and (ii) the date on which Tenant commences beneficial
use of the Premises. Tenant shall be deemed to have commenced beneficial use of
the Premises when Tenant has completed moving furniture and furnishings into the
Premises and is occupying all or substantially all of the Premises for purposes
of conducting business therein. Tenant and its contractors shall be allowed
access to the Premises approximately thirty (30) days prior to Landlord's
Anticipated Date of Substantial Completion of the Leasehold Work for the purpose
of installing Tenant's communication and data equipment and associated wiring
and to install other special equipment, fixtures and furniture, and such
installations shall not be considered the commencement of beneficial use of the
Premises by Tenant. Landlord shall use reasonable efforts to provide Tenant with
forty-five (45) days prior written notice of Landlord's Anticipated Date of
Substantial Completion. Any and all installations and other related activity by
Tenant or its contractors prior to the Lease Commencement Date shall be
coordinated with Landlord and its general contractor to insure that Tenant's
work in and to the Premises does not interfere with the work being performed by


                                       2
<PAGE>   5

Landlord and its contractors. Notwithstanding anything herein to the contrary,
neither Tenant nor its agents shall have access to the Premises during such
times specified by Landlord as times that Landlord or its Contractor reasonably
determine are likely to cause delay or interference with the activities of or on
behalf of Landlord in the Premises. All terms and conditions of this Lease,
including, without limitation, the insurance, release and waiver of liability
provisions of Articles XIII and XV hereof shall apply to and be effective during
such period of occupancy by Tenant, except for Tenant's obligation to pay rent.
Notwithstanding the foregoing, if Landlord is delayed in completing the
Leasehold Work as a result of a Tenant Delay (as defined in Exhibit B) then for
purposes of determining the Lease Commencement Date, the Leasehold Work shall be
deemed to have been substantially completed on the date that Landlord's
architect or contractor determines, in its reasonable, professional judgment,
that the Leasehold Work would have been substantially completed if such Tenant
Delay or Delays had not occurred.

     2.3 Promptly after the Lease Commencement Date is ascertained, Landlord and
Tenant shall execute, in recordable form, a written declaration setting forth
the Lease Commencement Date, the date upon which the initial term of this Lease
will expire, and the other information set forth therein. The form of such
declaration is attached hereto as Exhibit D, and is made a part hereof.

     2.4 (a) Landlord presently anticipates that, provided Tenant timely
complies with all its obligations under the Lease, including but not limited to
those set forth in Exhibit B, the Premises will be ready for occupancy by Tenant
and the Lease Commencement Date will occur on or about, but not before, April
15, 2001. In the event the Lease Commencement Date is delayed, regardless of the
reasons or causes of such delay, this Lease shall not be rendered void or
voidable as a result of such delay, and the term of this Lease shall commence on
the Lease Commencement Date as determined pursuant to Section 2.2 hereof.
Furthermore, except as expressly provided in this Section 2.4, Landlord shall
not have any liability whatsoever to Tenant on account of any such delay.

         (b) Notwithstanding anything to the contrary set forth in this Article
II, in the event that the construction, modification, renovation and
installation of the Initial Tenant Improvements in the Premises is not
substantially complete on or before one hundred twenty (120) days after the
anticipated date of substantial completion set forth in the Construction
Schedule (the "Anticipated Date of Substantial Completion") except as otherwise
provided below, Tenant, at its sole option, shall have the right to terminate
this Lease by delivering written notice of the exercise of such right of
termination to Landlord. Tenant's right to terminate this Lease in accordance
with the provisions of this Section 2.4(b) may be exercised by Tenant only
during the ten (10) business day period commencing on the one hundred
twenty-first (121st) day after the Anticipated Date of Substantial Completion
and terminating on the tenth (10th) business day after the one hundred
twenty-first (121st) day after the Anticipated Date of Substantial Completion
and if such right is not exercised by 5:00 p.m. on the tenth (10th) business day
after the one hundred twenty-first (121st) day after the Anticipated Date of
Substantial Completion, such right of termination shall lapse and expire and be
of no further force and effect. In the event this Lease is terminated pursuant
to this Section 2.4(b), this Lease shall be null and void and the parties shall
be released and discharged from further liabilities, obligations or
responsibilities hereunder and Landlord will return to Tenant all sums paid to
Landlord in accordance with


                                       3
<PAGE>   6

Section 3.1 below and the Letter of Credit delivered in accordance with Section
5.1 below. Notwithstanding the foregoing, Tenant shall not have the right to
terminate this Lease pursuant to this Section 2.4(b) if any of the following
provisions are applicable:

             (i) if the delay in completion is a result of more than five (5)
             days of Tenant Delay; or

             (ii) if Landlord certifies in writing and in good faith to Tenant,
             on or before one hundred twenty (120) days after the Anticipated
             Date of Substantial Completion that the Initial Tenant Improvements
             in the Premises will be substantially completed not later than one
             hundred fifty (150) days after the Anticipated Date of Substantial
             Completion, except for punch list items, the completion of which
             will not substantially interfere with the normal conduct of
             Tenant's business, and long-lead time items which have been
             identified to Tenant in accordance with the provisions of Exhibit
             B.

         (c) Notwithstanding anything to the contrary set forth above, in the
event that construction of the Initial Tenant Improvements in the Premises is
not substantially complete on or before one hundred fifty (150) days after the
Anticipated Date of Substantial Completion, except (i) for punch list items, the
completion of which will not substantially interfere with the normal conduct of
Tenant's business, (ii) long-lead items which have been identified to Tenant in
accordance with the provisions of Exhibit B and (iii) as otherwise provided in
this Section 2.4(c), Tenant, at its sole option, shall have the right to
terminate this Lease by delivering written notice of the exercise of such right
of termination to Landlord. Tenant's right to terminate this Lease in accordance
with the provisions of this Section 2.4(c) may be exercised by Tenant only
during the ten (10) business day period commencing on the one hundred
fifty-first (151st) day after the Anticipated Date of Substantial Completion and
if such right is not exercised by Tenant by 5:00 p.m. on the tenth (10th)
business day after the one hundred fiftieth (150th) day after the Anticipated
Date of Substantial Completion, such right of termination shall lapse and expire
and be of no further force and effect. In the event this Lease is terminated
pursuant to this Section 2.4(c), this Lease shall be null and void and the
parties shall be released and discharged from further liabilities, obligations
or responsibilities hereunder and Landlord will return to Tenant all sums and
letters of credit paid or delivered to Landlord concurrently with the signing of
this Lease pursuant to Sections 3.1(a) and 5.1 hereof. Notwithstanding the
foregoing, the one hundred fifty day period set forth above shall be extended on
a day-for-day basis up to an additional thirty (30) days if the delay in
substantial completion is the result of Tenant Delay as defined in Exhibit B
attached hereto. Thereafter, Tenant shall not have the right to terminate this
Lease pursuant to this Section 2.4(c) if the delay in substantial completion
extends beyond one hundred eighty (180) days as a result of Tenant Delay.

     2.5 For purposes of this Lease, the term "LEASE YEAR" shall mean a period
of twelve (12) consecutive calendar months, commencing on the first day of the
month in which the Lease Commencement Date occurs and each successive twelve
(12) month period, except that if the Lease Commencement Date shall occur on a
date other than the first day of a month, then the


                                       4
<PAGE>   7

first Lease Year shall also include the period from the Lease Commencement Date
to the first day of the following month.

                                   ARTICLE III
                                    BASE RENT

     During the Lease Term, Tenant shall pay to Landlord as annual base rent
(used interchangeably as "BASE RENT" or "BASE RENT") for the Premises, without
set off, deduction or demand, except as expressly provided in Section 14.3,
Article XVII and Article XVIII below, an amount equal to the product of
Thirty-One Dollars ($31.00) multiplied by the total number of square feet of
rentable area in the Premises as set forth in Section 1.1 above and as may be
adjusted in accordance with the provisions of Section 1.3, which amount may be
increased in accordance with the provisions of Paragraph 8(b) of the Work
Agreement hereof and which amount, as it may be increased, shall be subject to
annual adjustment as provided in Section 3.2. The annual base rent payable
hereunder during each Lease Year shall be divided into equal monthly
installments and such monthly installments shall be due and payable in advance
on the first day of each month during such Lease Year. Concurrently with the
signing of this Lease, Tenant shall pay to Landlord the sum of Two Hundred
Forty-Two Thousand One Hundred Forty-Eight Dollars and Seventy-Five Cents
($242,148.75) which sum shall be credited by Landlord toward the first monthly
installment of annual base rent due for the first calendar month falling within
the Lease Term. If the Lease Term begins on a date other than on the first day
of a month, rent from such date until the first day of the following month shall
be prorated on a per diem basis at the base rate payable during the first Lease
Year, and such prorated rent shall be payable from the amount delivered to
Landlord in accordance with the preceding sentence.

     3.2 (a) Commencing on the first (1st) day of the second (2nd) Lease Year
and on the first day of each and every Lease Year thereafter during the initial
Lease Term, the annual base rent shall be increased by the lesser of (a) two and
one-half percent (2.5%) of the amount of annual base rent payable for the
immediately preceding Lease Year and (b) the increase in the Consumer Price
Index ("CPI"), calculated as set forth below, multiplied by three hundred
percent (300%).

         (b) Commencing on the first (1st) day of the second (2nd) Lease Year
and on the first day of each and every Lease Year thereafter during the initial
Lease Term, annual increases in the CPI shall be calculated in the following
manner:

             (1) The Revised Consumer Price Index for Urban Wage Earners and
             Clerical Workers, "November" 1996=100 Base, Base Year, All Items,
             Washington-Baltimore, DC-MD-VA Metropolitan Area (CPI-W), as
             published by the Bureau of Labor Statistics of the United States
             Department of Labor (herein referred to as the "Index"), which is
             published for the period that includes the month immediately
             preceding the first day of the Lease Year for which such CPI
             Adjustment is being made (herein referred to as the "Adjustment
             Index"), shall be compared with the Index published for the period
             that includes the month


                                       5
<PAGE>   8

             immediately preceding the month in which the Lease Commencement
             Date occurs (herein referred to as the "Beginning Index"). If the
             Adjustment Index has increased over the Beginning Index, the
             percentage increase between the Beginning Index and the Adjustment
             Index shall be determined.

             (2) The percentage increase determined in Step (1) above shall be
             multiplied by three hundred percent (300%). The resulting
             percentage shall then be multiplied by the annual base rent for the
             first Lease Year set forth in Section 3.1 hereof to arrive at the
             amount of the increase in annual base rent for the Lease Year for
             which such adjustment is being determined.

             (3) The CPI Adjustment determined in Step (2) above shall be added
             to the annual base rent for the first Lease Year set forth in
             Section 3.1 to arrive at the adjusted annual base rent payable for
             the Lease Year for which the adjustment is being made. In the event
             the annual base rent as adjusted pursuant to the procedure set
             forth in Steps (1) and (2) above is less than the amount of annual
             base rent payable for the immediately preceding Lease Year
             increased by two and one-half percent (2.5%) then the annual base
             rent shall be the adjusted annual base rent shall be as calculated
             pursuant to Steps (1), (2) and (3) which rent shall be payable in
             equal monthly installments in advance on the first day of each
             month of such Lease Year.

         (c) If the Index is changed so that a base year other than "November"
1996=100 is used, the Index used herein shall be converted in accordance with
the conversion factor published by the Bureau of Labor Statistics of the United
States Department of Labor. If the Index is discontinued or otherwise revised
during the Lease Term, such other government index or computation with which it
is replaced shall be used in order to obtain substantially the same result as
would be obtained if the Index had not been discontinued or revised.

         (d) Promptly after the adjustment in the annual base rent is determined
for each Lease Year, Landlord shall submit to Tenant a statement setting forth
the amount of such adjustment and the computations by which it was determined.
Since the actual increase in the annual base rent may not be determined until
after the start of a new Lease Year, until the actual increase in the annual
base rent is determined, Tenant shall make estimated monthly payments of base
rent during such Lease Year in an amount based upon Landlord's reasonable
estimate of the monthly installments of base rent that will be payable during
such Lease Year. Promptly after receipt of a statement from Landlord setting
forth the actual increase in the monthly installments of base rent for such
Lease Year, the difference between the estimated monthly payments paid by Tenant
and the actual amount of base rent determined to be owing for such months shall
be determined. If the estimated payments by Tenant exceed the actual amount
determined to be owing, the excess shall be credited against the next monthly
installment(s) of base rent falling due hereunder. If the actual amount
determined to be owing is greater than Tenant's estimated


                                       6
<PAGE>   9

payments, the deficiency shall be paid by Tenant together with the next monthly
installment of base rent due hereunder.

         (e) The provisions of this Section 3.2 shall not be applicable to the
Renewal Term unless agreed to or so determined in accordance with the provisions
of Rider No. 1.

     3.3 All rent shall be paid to Landlord in legal tender of the United States
at P.O. Box 3557, Boston, MA 022441-3557, or to such other party or to such
other address as Landlord may designate from time to time by written notice to
Tenant. If Landlord shall at any time accept rent after it shall become due and
payable, such acceptance shall not excuse a delay upon subsequent occasions, or
constitute or be construed as a waiver of any of Landlord's rights hereunder. If
any sum payable by Tenant under this Lease is paid by check which is returned
due to insufficient funds, stop payment order, or otherwise, then: (a) such
event shall be treated as a failure to pay such sum when due; and (b) in
addition to all other rights and remedies of Landlord hereunder, Landlord shall
be entitled to impose a returned check charge of Fifty Dollars ($50.00) to cover
Landlord's administrative expenses and overhead for processing.

     3.4 Landlord and Tenant agree that no rental or other payment for the use
or occupancy of the Premises is or shall be based in whole or in part on the net
income or profits derived by any person or entity from the Building or the
Premises. In the event the holder of any mortgage or deed of trust secured by
the Building acts as landlord under this Lease or otherwise owns or holds title
to the Building by foreclosure or deed-in-lieu of foreclosure, Tenant further
agrees that it will not enter into any sublease, license, concession or other
agreement for any use or occupancy of the Premises which provides for a rental
or other payment for such use or occupancy based in whole or in part on the net
income or profits derived by any person or entity from the Premises so leased,
used or occupied. Nothing in the foregoing sentence, however, shall be construed
as permitting or constituting Landlord's approval of any sublease, license,
concession, or other use or occupancy agreement not otherwise permitted or
approved by Landlord in accordance with the provisions of Article VII.

                                   ARTICLE IV
                                 ADDITIONAL RENT

     4.1 Operating Expenses.

         (a) (i) Commencing on the first (1st) anniversary of the Lease
Commencement Date and continuing with each month thereafter during the Lease
Term, Tenant shall pay Landlord, as additional rent for the Premises, Tenant's
proportionate share of the amount by which actual operating expenses incurred by
Landlord in connection with the management, operation and ownership (with
respect to Real Estate Taxes, as defined in subsection (b) below) of the
Building and the parking deck ("OPERATING EXPENSES") during any calendar year
falling entirely or partly within the Lease Term exceed a base amount (the "Base
Year Operating Expenses") equal to the Operating Expenses incurred by Landlord
in connection with the management, operation and ownership of the Building
during the twelve month period (the "Base Year") commencing January 1, 2001, and
ending December 31, 2001. For purposes of this Article IV Tenant's proportionate
share of such increases in Operating Expenses shall be


                                       7
<PAGE>   10

that percentage which is equal to a fraction, the numerator of which is the
number of square feet of rentable area in the Premises and the denominator of
which is the total number of square feet of rentable area in the Building,
excluding the number of square feet devoted to storage space and parking. It is
understood that the number comprising such denominator is subject to change
because of changes in the use or configuration of space in the Building or the
addition of space to the Building or the deletion of space from the Building or
in the amount of space leased by tenants who pay by separate meter for their
electrical and/or janitorial, cleaning, or other utilities or services so that
Tenant actually pays its fair share of Operating Expenses; provided, however,
that any such change in rentable area shall be determined in accordance with the
standard set forth in Section 1.3 of this Lease. Tenant's proportionate share
shall increase in the event Tenant expands the Premises during the Lease Term.

         (ii) For purposes of calculating the Base Year Operating Expenses, the
line item component for Real Estate Taxes shall be the amount of Real Estate
Taxes incurred by Landlord in the first year the Building is fully assessed for
tax purposes as reasonably calculated by Landlord, but not later than tax year
2003 (i.e. July 1, 2003 - June 30, 2004). Until such amount is finally
determined, Tenant shall pay amounts due pursuant to this Article based on
Landlord's reasonable estimate and at such time as the base tax amount is
finally determined, Landlord shall notify Tenant thereof in writing, which
writing shall specify the amount of Tenant's actual liability under this Article
prior to the date of the statement and the amount actually paid by Tenant under
this Article during such period. Landlord has previously provided Tenant with
its current estimate of Base Year Real Estate Taxes. Tenant acknowledges that
such estimate is no more than Landlord's reasonable belief of the Real Estate
Taxes that will be imposed on the Building and the land upon which the Building
is constructed and that the actual amount of Base Year Real Estate Taxes may be
higher or lower than Landlord's estimate. Landlord shall credit any overpayment
toward sums next coming due under this Article and Tenant shall reimburse
Landlord as additional rent for any underpayments during such period.

         (iii) Landlord agrees that no item of maintenance or repair or any the
provision of any service will be deferred in the Base Year solely for the
purposes of reducing Base Year Operating Expenses. The specific obligations of
Tenant with respect to such increases shall be governed by the remaining
sections of this Article IV. Operating Expenses shall be calculated consistently
from year to year during the Lease Term.

     (b) The Operating Expenses shall be determined on a calendar year, accrual
basis and shall include the costs and expenses actually incurred by Landlord in
accordance with sound management practices generally prevailing for first-class
office buildings in the North Bethesda/Rockville, Maryland area described in
subsection (1) below, but shall not include the costs and expenses described in
subsection (2) below.



                                       8
<PAGE>   11

         (1) Included costs and expenses:

             (i) Actual gas, water, sewer, electricity and other utility charges
         (including surcharges) of every type and nature consumed in connection
         with the operation of the Building.

             (ii) Insurance premiums paid by Landlord.

             (iii) Personnel costs of the Building, including, but not limited
         to, salaries, wages, fringe benefits and other direct and indirect
         costs of engineers, superintendents, watchmen, porters and any other
         personnel related to the management, maintenance, repair and operation
         of the Building but excluding the costs of any compensation paid to
         partners of Landlord or officers and directors of the managing agent
         and any separate charge for the overhead expenses attributable to
         maintaining an office for such partners, officers, or directors or any
         employee of the managing agent above the grade of superintendent or
         building manager; provided, however, that if during the Lease Term
         such personnel or entities are working on projects other than the
         Building, then their wages, salaries, fees and related expenses shall
         be appropriately allocated among all of such projects and only that
         portion of such expenses reasonably allocable to the Building shall be
         included as an Operating Expense.

             (iv) Costs of service and maintenance contracts, including, but not
         limited to, chillers, boilers, controls, elevators, mail chute,
         windows, security service, concierge, landscaping, snow and ice
         removal and management fees not to exceed (I) during the initial five
         (5) Lease Years, in excess of three percent (3%) of the gross revenues
         payable to Landlord in connection with the Building during the
         applicable calendar year and (II) during the remaining five (5) Lease
         Years, in excess of four percent (4%) of the gross revenues payable to
         Landlord in connection with the Building during the applicable
         calendar year.

             (v) Except to the extent specifically excluded by subsection (2)
         below, all other maintenance and repair expenses and supplies which
         are deducted by Landlord in computing its Federal income tax
         liability.

             (vi) Depreciation (on a straight-line basis over the shorter of the
         actual payback period of the improvement and the estimated useful life
         of the improvement commencing in the calendar year in which the
         improvement was substantially competed, with interest at Landlord's
         cost of funds, or it the


                                       9
<PAGE>   12

         improvement is not financed, at the prime rate reported in The Wall
         Street Journal on the date of such expenditure) for capital
         expenditures made by Landlord (A) after the first two (2) Lease Years
         to reduce operating expenses if Landlord reasonably believes that the
         annual reduction in operating expenses will exceed depreciation
         therefor or (B) to comply with the Legal Requirements (as defined in
         Section 6.1 below) promulgated after the Lease Commencement Date.

             (vii) Any other costs and expenses reasonably incurred by Landlord
         in maintaining or operating the Building, except as provided in
         subsection (2) below.

             (viii) The costs of any additional services not provided to the
         Building during the Base Year but thereafter provided by Landlord in
         the prudent management of the Building if comparable services are
         being furnished at first class buildings in the vicinity of the
         Building, but only to the extent of any increase in the costs to
         provide such additional service over the costs to provide such service
         during the first calendar year in which the same was provided to the
         Building (except that if and to the extent any such service is in
         substitution for any service provided during the Base Year, then the
         entire cost thereof shall be included as an Operating Expense during
         each year the service is provided to the Building).

             (ix) Charges for concierge, security, access control, janitorial,
         char and cleaning services and supplies.

             (x) Real Estate Taxes (as hereinafter defined).

             (xi) Complex Common Expenses (as hereinafter defined).

             (xii) Notwithstanding anything set forth in subsection (2) below,
         the Building's share of all costs, expenses, charges or other
         assessments of The Preserve at Tower Oaks Office Park Association or
         other authority or entity or any successor thereto.

             (xiii) City of Rockville Transportation Management District fee (or
         any successor, replacement or similar fee), currently in the amount of
         Ten Cents ($0.10) per rentable square foot per annum, to be paid in
         equal monthly installments on the first (1st) day of each month.

             (xiv) Accounting expenses reasonably incurred by Landlord in
         calculating Operating Expenses and legal fees and


                                       10
<PAGE>   13

         expenses reasonably incurred by Landlord in connection with
         proceedings undertaken to reduce Operating Expenses.

         (2) Excluded costs and expenses:

             (i) Principal or interest payments on and any other charges paid by
         Landlord in connection with any mortgages, deeds of trust or other
         financing encumbrances.

             (ii) Rental payments (including percentage rent and any increases
         in base rent) made under any ground lease, except to the extent such
         rental payments represent payment of Real Estate Taxes (as hereinafter
         defined) and are included in the line item component attributable to
         Base Year Real Estate Taxes.

             (iii) Leasing commissions payable by Landlord and advertising and
         promotional expenditures associated with marketing vacant space in the
         Building.

             (iv) Deductions for depreciation for the Building, except to the
         extent included in subsection (1) above.

             (v) Capital improvements, including, without limitation, renovation
         of the common areas of the Building, that are not deducted by Landlord
         in computing its federal income tax liability, except to the extent
         included in subsection (1) above.

             (vi) The costs of special services, tenant improvements and
         concessions, repairs, maintenance items or utilities separately
         chargeable to, or specifically provided for, individual tenants of the
         Building, including, without limitation, the cost of preparing any
         space in the Building for occupancy by any tenant and/or for altering,
         renovating, repainting, decorating, planning and designing spaces for
         any tenant in the Building in connection with the renewal of its lease
         and/or costs of preparing or renovating any vacant space for lease in
         the Building (including permit, license and inspection fees).
         Notwithstanding the foregoing, the provision of services and utilities
         to other tenants of the Building during hours set forth in Section
         14.1 shall be fully includable in Operating Expenses.

             (vii) Attorney's fees and disbursements, recording costs, mortgage
         recording taxes, title insurance premiums, title closer's gratuity and
         other similar costs, incurred in connection with any mortgage
         financing or refinancing or execution, modification or


                                       11
<PAGE>   14

         extension of any ground lease; loan prepayment penalties, premiums,
         fees or charges.

             (viii) Salaries and all other compensation (including fringe
         benefits and other direct and indirect personnel costs ) of partners,
         officers and executives above the grade of superintendent or building
         manager of Landlord or the managing agent.

             (ix) The costs of repairs, replacements and alterations for which
         and to the extent that Landlord is actually reimbursed therefor from
         any source; it being understood that any rent payments or other
         payments by tenants in the nature of additional rent as provided in
         this Section 4.1 shall not be deemed sources of reimbursement to
         Landlord for such costs.

             (x) Fees, costs and expenses incurred by Landlord in connection
         with or relating to claims against or disputes with tenants of the
         Building or the negotiation of leases with tenants or prospective
         tenants, including, without limitation, legal fees and disbursements.

             (xi) Costs incurred by Landlord for the original construction and
         development of the Building and nonrecurring costs and expenses
         incurred by Landlord in curing, repairing or replacing any structural
         portion of the Building or any of the base building mechanical,
         electrical, plumbing or fire and life safety systems made necessary as
         a result of defects in design, workmanship or materials.

             (xii) Any costs and expenses incurred by Landlord in connection
         with causing the common and public areas of the Building which are
         within Landlord's sole and exclusive control to comply with applicable
         Legal Requirements, except to the extent included in subsection 1
         above.

             (xiii) The costs of all paintings, sculptures or other works of art
         (other than insurance and maintenance costs therefor).

             (xiv) Costs and expenses incurred by Landlord for services that are
         duplicative of or are normally included in any management fees paid by
         Landlord.

             (xv) That portion of any Operating Expenses which is paid to any
         entity affiliated with Landlord which is in excess of the amount which
         would otherwise be paid to an entity which is not affiliated with
         Landlord for the provision of the same service.


                                       12
<PAGE>   15

             (xvi) Sums paid by Landlord for any indemnity, damages, fines, late
         charges, penalties or interest for any late payment or to correct
         violations of building codes or other laws, regulations or ordinances
         applicable to the Building, except for expenditures for repairs,
         maintenance and replacement or other items that would otherwise
         reasonably constitute Operating Expenses.

             (xvii) Costs attributable to any "tap fees" or one-time lump sum
         sewer or water connection fees payable in connection with the initial
         construction of the Building.

             (xviii) Costs and expenses incurred by Landlord in connection with
         damage, casualty or condemnation of all or a portion of the Building;
         provided, however, that for so long as Boston Properties Limited
         Partnership or an affiliate thereof is the owner or manager of the
         Building, with respect to the cost to repair damage, Landlord may
         include in Operating Expenses (1) the amount of a commercially
         reasonable deductible applied to each such occurrence and (2) if
         Landlord determines, in its reasonable judgment, that the effect of
         making a claim under Landlord's insurance policy or policies would be
         to increase, in the aggregate, the future cost of insurance premiums
         and repair and maintenance expenses relating to the Building, Landlord
         may include in Operating Expenses the cost to repair such damage to
         the extent such cost does not exceed two hundred percent (200%) of the
         deductible amount applicable under Landlord's insurance policy or
         policies to such occurrence in any calendar year; provided, however,
         that Landlord may only include such cost in Operating Expenses, if
         Landlord actually makes such repair and does not submit an insurance
         claim in connection therewith.

             (xix) Rental for personal property leased to Landlord except for
         rent for personal property leased to Landlord the purchase price for
         which, if purchased, would be fully includable in Operating Expenses
         in the year of purchase.

             (xx) Any costs actually reimbursed under the warranty of any
         general contractor, subcontractor or supplier and realized by
         Landlord.

             (xxi) Reserves established by Landlord for bad debts or rent losses
         attributable to tenants of the Building and/or for repairs,
         maintenance and replacements.


                                       13
<PAGE>   16

             (xxii) Costs and expenses attributable to management fees (I)
         during the initial five (5) Lease Years, in excess of three percent
         (3%) of the gross revenues payable to Landlord in connection with the
         Building during the applicable calendar year and (II) during the
         remaining five (5) Lease Years, in excess of four percent (4%) of the
         gross revenues payable to Landlord in connection with the Building
         during the applicable calendar year.

             (xxiii) Attorney's fees and disbursements, brokerage commissions,
         transfer taxes, recording costs and taxes, title insurance premiums,
         title closer's fees and gratuities and other similar costs incurred in
         connection with the sale or transfer of an interest in Landlord or the
         Building.

             (xxiv) Landlord's general overhead costs and costs and expenses of
         administration and management of partnership activities of Landlord.

             (xxv) Any costs or expenses related exclusively to retail space in
         the Building which are in excess of normal office use; it being
         understood that any cost or expense related to, inter alia, the
         Building exterior (except for store windows), the lobby or elevators,
         do not relate exclusively to retail space and are fully includable in
         Operating Expenses to the extent otherwise permitted hereunder.

             (xxvi) Salaries and all other compensation of employees of Landlord
         or the managing agent to the extent that such employees devote
         portions of their time to the operation and management of buildings
         other than the Building.

             (xxvii) Costs and expenses attributable to any testing,
         investigation, management, maintenance, remediation or removal of
         Hazardous Materials, as defined in this Lease (other than any testing
         or monitoring customarily conducted by owners of building comparable
         to the Building n the ordinary course of operating the same).

             (xxviii) Costs and expenses attributable to the operation and
         maintenance of the Shower Facility, the Parking Deck and the surface
         parking lot servicing the Building.

     In the calculation of any Operating Expenses hereunder, it is understood
that no expense shall be charged more than once.


                                       14
<PAGE>   17

         (b) As used above, the term "REAL ESTATE TAXES" shall mean (i) all real
estate taxes, including general and special assessments, if any, which are
imposed upon Landlord or assessed against the Building or the Land upon which
the Building is situated; (ii) any other present or future taxes or governmental
charges that are imposed upon Landlord or assessed against the Building or the
Land, including, but not limited to, any tax levied on or measured by the rents
payable by tenants of the Building, which are in the nature of, or in
substitution for, real estate taxes; (iii) all taxes which are imposed upon and
paid by Landlord, and which are assessed against the value of any improvements
to the Premises made by Tenant or any machinery, equipment, fixtures or other
personal property of Tenant used therein and (iv) expenses (including reasonable
attorneys' fees) incurred in reviewing, protesting or seeking a reduction of
real estate taxes. If any of the buildings that may comprise the Complex are
assessed together then Real Estate Taxes for the Building shall be a fraction
thereof, the numerator of which is the number of square feet of rentable area in
the Building and the denominator of which is the number of square feet of
rentable area in the Complex; provided, however, that Tenant shall not pay as a
result of such aggregating such buildings more than it would have otherwise paid
were all such buildings constructed on separate tax lots. Real Estate Taxes
shall not include (I) any rental or other charges or fee imposed upon Landlord
in connection with the lease or use of any vault space or (II) any income taxes,
excess profits taxes, excise taxes, franchise taxes, estate taxes, inheritance
taxes, gift taxes, succession taxes and transfer taxes, except to the extent any
of such taxes are in the nature of or are in substitution for or
recharacterization or replacement of Real Estate Taxes.

         (c) Landlord and Tenant agree that the Real Estate Taxes for the first
(1st) six (6) tax years of the Lease Term may be reduced (the "Tax Reduction")
by application of the provisions of Sections 52-69 through 52-79 of the
Montgomery County Code (1998 L.M.C., ch. 9, Section 1) and Section 9-230 of the
State of Maryland Tax-Property Article which are intended to benefit office
tenants in the State of Maryland and Montgomery County. Landlord agrees that on
the later to occur of (i) October 31 of each of those tax years and (ii) thirty
(30) days following the date Landlord actually obtains the benefit of the Tax
Reduction resulting directly from the application of the laws described herein
to Tenant's business operations in the Building, Landlord, at Landlord's
election either shall pay Tenant the amount of the Tax Credit or shall direct
Tenant to deduct the amount of the Tax Reduction from its next estimated payment
or payments of base rent and additional rent due under this Lease. In the event
Landlord timely fails to notify Tenant of Landlord's election as described in
the preceding sentence, Tenant may deduct the amount of the Tax Reduction from
its next estimated payment or payments of base rent and additional rent due
under this Lease. It is expressly agreed that in order to avoid duplication of
the benefit to Tenant resulting from the Tax Reduction, the computation of Real
Estate Taxes for the purposes of this Article IV, including for the calculation
made for purposes of determining the Base Year Real Estate Taxes, shall be made
without regard to the Tax Reduction (i.e. Tenant's obligations under this
Article IV shall be computed using the gross amount of Real Estate Taxes before
the Tax Reduction). Tenant shall only be entitled to the Tax Reduction arising
directly from Tenant's business operations in the Building and shall not be
entitled to any similar Tax Reduction arising from or attributable any other
tenant's or occupant's conduct of business in the Building or otherwise.
Notwithstanding anything herein to the contrary, in no event shall the Tax
Reduction attributable to any calendar year cause the applicable line item
component for Real Estate Taxes to fall below the applicable

                                       15
<PAGE>   18
line item for Real Estate Taxes in the Base Year. Landlord shall cooperate with
Tenant at Tenant's sole cost and expense in obtaining the Tax Reduction.

         (d) As used above, the term "COMPLEX COMMON EXPENSES" shall mean those
Operating Expenses incurred by Landlord in owning, operating and/or managing the
Complex (as opposed to those Operating Expenses related exclusively to the
Building) including any fees, costs or assessments allocated to the Building
under any agreement encumbering the Building, but only a fraction of such
expenses, the numerator of which is the number of square feet of rentable area
in the Building and the denominator of which is the number of square feet of
rentable area in the Complex.

         (e) Notwithstanding anything to the contrary in this Article IV, Tenant
shall not be obligated to pay to Landlord increases of additional rent for any
calendar year after the first Lease Year attributable to Controllable Operating
Expenses (as defined in the next sentence) which exceed eight percent (8%), in
the aggregate, of the amount of additional rent attributable to Controllable
Operating Expenses for the immediately preceding calendar year. For the purposes
of this Section, Controllable Operating Expenses are all Operating Expenses
other than Operating Expenses incurred by Landlord which are attributable to (i)
Real Estate Taxes, (ii) utilities, (iii) snow removal and (iv) insurance.

     4.2 In the event the average occupancy rate for the entire Building shall
be less than one hundred percent (100%) or if any tenant is paying separately
for electricity or other utilities or services for any calendar year, including
the Base Year, for purposes of calculating the additional rent payable by Tenant
pursuant to this Article IV for each calendar year, the Operating Expenses for
the Base Year and such calendar year that fluctuate depending on the level of
occupancy of the Building shall each be increased by the amount of additional
costs and expenses that Landlord reasonably estimates would have been incurred
if the average occupancy rate for the entire Building had been one hundred
percent (100%) and as if no tenants had separately paid for electricity or other
utilities and services for the Base Year and such calendar year. In addition,
when calculating the Operating Expenses for the Base Year, Landlord shall take
into account and shall make appropriate adjustments (a) to reflect (i) its
reasonable estimation of the impact that warranties and guaranties in effect in
connection with the initial construction of the Building have in reducing the
costs that Landlord would otherwise have paid for such services during the Base
Year and (ii) the fact that the Building will be partially occupied and in
operation only during a portion of the Base Year and (iii) to calculate Base
Year Operating Expenses as if the Building were 100% occupied and in full
operation from January 1 through December 31, 2001. It is the intent of this
provision to permit Landlord to recover for increases in Operating Expenses that
fluctuate based on occupancy attributable to occupied space in the Building even
though the aggregate of such expenses shall have been reduced as a result of
vacancies in the Building.

     4.3 At the beginning of calendar year 2002 and each calendar year
thereafter during the Lease Term, Landlord shall submit to Tenant a reasonably
detailed statement setting forth Landlord's reasonable estimate of the amount by
which the Operating Expenses that are expected to be incurred during such
calendar year will exceed the Base Year Operating Expenses, and the computation
of Tenant's proportionate share of such anticipated increase. Except as
otherwise


                                       16
<PAGE>   19

provided herein, Tenant shall pay to Landlord commencing on the first (1st) day
of the second (2nd) Lease Year and on the first day of each month during the
calendar year in which the first (1st) day of the second (2nd) Lease Year occurs
and thereafter following receipt of such statement during each calendar year
during the remainder of the Lease Term, an amount equal to Tenant's
proportionate share of the anticipated increase in such expenses multiplied by a
fraction, the numerator of which is 1, and the denominator of which is the
number of months during such calendar year which fall within the Lease Term and
follow the date of the foregoing statement. Within one hundred twenty (120) days
after the expiration of each calendar year falling entirely or partly within the
Lease Term, Landlord shall submit to Tenant a reasonably detailed statement
showing (i) the actual amount of Base Year Operating Expenses, (ii) the actual
Operating Expenses paid or incurred by Landlord during the immediately preceding
calendar year, (iii) a computation of Tenant's proportionate share of the amount
by which the Operating Expenses actually incurred during the preceding calendar
year exceeded the Base Year Operating Expenses, and (iv) the aggregate amount of
the estimated payments made by Tenant on account thereof. If the aggregate
amount of such estimated payments exceeds Tenant's actual liability for such
increases, Tenant shall deduct the net overpayment from its next estimated
payment or payments due under Article III above or this Article IV for the then
current year. If Tenant's actual liability for such increases exceeds the
estimated payments made by Tenant on account thereof, then Tenant shall promptly
pay to Landlord the total amount of such deficiency as additional rent due
hereunder.

     4.4 In the event the Lease Term begins or expires on a day other than the
first or last day of a calendar year, the increases in the Operating Expenses
for such calendar year shall be apportioned by multiplying the amount of
Tenant's proportionate share thereof for the full calendar year by a fraction,
the numerator of which is the number of days during such calendar year falling
within the Lease Term, and the denominator of which is 365.

     4.5 All payments required to be made by Tenant pursuant to this Article IV
shall be paid to Landlord, without setoff or deduction, in the same manner as
annual base rent is payable pursuant to Article III hereof.

     4.6 Tenant's liability for its proportionate share of the increases in
Operating Expenses described in Section 4.1 hereof for the last calendar year
falling entirely or partly within the Lease Term shall survive the expiration of
the Lease Term. Similarly, Landlord's obligation to refund to Tenant the excess,
if any, of the amount of Tenant's estimated payments on account of such
increases for such last calendar year over Tenant's actual liability therefor
shall survive the expiration of the Lease Term and such refund shall be made to
Tenant within thirty (30) days of the date of Landlord's calculation of the
actual increases for such last calendar year falling entirely or partly within
the Lease Term.

     4.7 In the event that Tenant, in good faith, believes that the amounts paid
by Tenant to Landlord relating to increases in Operating Expenses during any
calendar year falling within the Lease Term exceeded the amounts to which
Landlord was entitled to hereunder then, Tenant or an independent, certified
public accountant designated by Tenant (who is hired by Tenant on a
noncontingency basis and provides a full range of accounting services) shall
have the right, during regular business hours and after giving ten (10) business
days' advance written notice to


                                       17
<PAGE>   20

Landlord, to inspect and audit Landlord's books and records relating to such
charges for a period of two (2) years with respect to the Base Year and one (1)
year for each calendar year thereafter following the receipt by Tenant of the
statement required of Landlord pursuant to Section 4.3 hereof for such calendar
year. If Landlord agrees that such audit or audited statement shows that the
amounts paid by Tenant to Landlord on account of increases in such charges
exceeded the amounts to which Landlord was entitled hereunder, or that Tenant is
entitled to a credit with respect to any such charges, Landlord shall promptly
refund to Tenant the amount of such excess or the amount of such credit, as the
case may be. Tenant shall (and shall cause its agents to) keep the results of
such audit or audited statement strictly confidential. All costs and expenses of
any such audit shall be paid by Tenant, except that if such audit shows that
Tenant's obligations to Landlord under this Article IV were overstated by
Landlord by more than four percent (4%), Landlord shall reimburse Tenant for the
reasonable out-of-pocket costs and expenses incurred by Tenant in such audit, up
to a maximum of Seven Thousand Five Hundred Dollars ($7,500.00); provided that
in no event shall Landlord be obligated to reimburse Tenant with respect to any
calendar year for such expenses in any amount that exceeds the amount of the
reimbursement due to Tenant on account of any overpayment. If Tenant does not
notify Landlord in writing of any objection to any statement within said two (2)
year or one (1) year period, as applicable, then Tenant shall be deemed to have
waived such objection.

     4.8 Notwithstanding anything in this Article IV to the contrary, if
Landlord appeals Real Estate Taxes and obtains a refund for any calendar year in
which Tenant paid increases in Real Estate Taxes pursuant to this Article, then
Landlord shall promptly pay to Tenant its proportionate share of such refund
(after deducting the reasonable expenses incurred by Landlord in obtaining such
refund to the extent not otherwise included in Real Estate Taxes) based upon the
proportion that the line item component attributable to Real Estate Taxes paid
by Tenant for the period to which such refund relates bears to the total amount
of the line item component attributable to Real Estate Taxes during the calendar
year to which such refund relates; provided, however, in no event shall the
amount of Tenant's proportionate share of such refund be greater than the total
amounts paid to Landlord by Tenant pursuant to this Article on account of
increases in Operating Expenses with respect to the calendar year to which such
statement relates. Landlord and Tenant agree that if the refund is for a
calendar year in which Real Estate Taxes incurred by Landlord did not exceed the
Base Year Real Estate Taxes (i.e., Tenant did not pay any increases in Real
Estate Taxes pursuant to this Article for such calendar year), then Tenant shall
not be entitled to a proportionate share of such refund. Subject to the gross-up
provisions of Section 4.2 above, if Landlord contests the Real Estate Taxes for
a calendar year within twelve (12) months of Landlord's receipt of the
applicable Real Estate Tax bill, and such contest results in either an increase
in the line item component attributable to Real Estate Taxes for such calendar
year or an increase or decrease in the line item component attributable to Base
Year Real Estate Taxes, as applicable, Landlord shall bill Tenant for prior
underpayments of Real Estate Taxes thereby resulting and the line item component
attributable to Base Year Real Estate Taxes shall be reduced or increased
accordingly.


                                       18
<PAGE>   21

                                    ARTICLE V
                                SECURITY DEPOSIT

     5.1 (a) Simultaneously with Tenant's execution of this Lease, Tenant shall
deliver to Landlord the sum of Two Million Eight Hundred Twelve and Fifty
Dollars ($2,812,050) (i.e. Thirty Dollars ($30.00) multiplied by the number of
square feet of rentable area in the Premises), as a security deposit
(hereinafter referred to as the "SECURITY DEPOSIT" or "SECURITY DEPOSIT"), which
sum shall be in addition to the amount paid by Tenant to Landlord pursuant to
Section 3.1 hereof. However, all cash which Tenant delivers to Landlord as a
security deposit, including the proceeds if Landlord draws on the Letter of
Credit (as defined below), will be deposited in an interest bearing account
maintained by Landlord (which account may also contain the security deposits of
other tenants or other sums) and such interest shall accrue to the benefit of
Tenant and be paid to Tenant annually, absent Tenant's default, beyond any
applicable notice and cure period, under this Lease. Landlord shall, in good
faith, deposit such cash in the highest yielding money market account or
certificate of deposit readily available at the bank or other institution at
which such cash portion of the Security Deposit is so maintained by Landlord.
Subject to the terms of the sentence which immediately precedes this sentence,
any cash portion of the Security Deposit held by Landlord shall accrue interest
at the rate of interest paid by the bank or other institution at which such cash
portion of the Security Deposit is maintained, and any such interest shall be
deemed to be a part of the Security Deposit. Among other things, Landlord has
assigned to the holder of the mortgage encumbering the Building, all of
Landlord's interest in this Lease, including, without limitation, the security
deposit; provided, however, that so long as Landlord is not in default beyond
any applicable notice and cure period under any loan secured by the Building,
Landlord shall retain possession of the Letter of Credit in its offices located
in the Washington, D.C. metropolitan area.

         (b) The security deposit shall be security for the performance by
Tenant of all of Tenant's obligations, covenants, conditions and agreements
under this Lease. Within thirty (30) days after the expiration of the Lease
Term, and provided Tenant has vacated the Premises and is not in default
hereunder, Landlord shall return the security deposit to Tenant, less such
portion thereof as Landlord shall have appropriated to satisfy any default by
Tenant hereunder. In the event of any monetary or other material default, beyond
any applicable notice and cure period, by Tenant under this Lease, Landlord
shall have the right, but shall not be obligated, to use, apply or retain all or
any portion of the security deposit for (i) the payment of any annual base rent
or additional rent or any other sum or amount which Tenant is obligated to pay
under the terms of this Lease or which Landlord has spent in accordance with the
terms of this Lease and as to which Tenant is in default beyond any applicable
notice and cure period and (ii) the payment of any amount which Landlord may
spend or become obligated to spend to repair physical damage to the Premises or
the Building pursuant to Section 8.2 hereof. If any portion of the security
deposit is so used or applied, within ten business (10) days after written
notice to Tenant of such use or application, Tenant shall deposit with Landlord
cash in an amount sufficient to restore the security deposit to its original
amount or shall likewise increase the amount of the Letter of Credit and
Tenant's failure to do so shall constitute a default under this Lease. Tenant
hereby authorizes Landlord to deposit the security deposit with the holder of
any mortgage (as defined in Section 21.1) if and to the extent required by said
holder; provided, however, that such holder shall hold the security deposit
subject to Tenant's rights with respect to


                                       19
<PAGE>   22

the security deposit set forth herein. Subject to the provisions of Section
5.1(a) above, if and to the extent required by the holder of any first mortgage
(as defined in Section 21.1), Tenant hereby authorizes Landlord to deposit the
security deposit with any such holder with whom Tenant has a non-disturbance
agreement (or from any such holder that agrees to execute a non-disturbance
agreement in accordance with Article XXI, even if Tenant fails to execute such
agreement and submit the same for such mortgage holder's execution, unless such
failure is solely because there is a bona fide dispute between Tenant, Landlord,
and/or the mortgage holder with respect to whether the proposed non-disturbance
agreement is in accordance with Article XXI (in which event Landlord shall not
deposit the security deposit with such mortgage holder until such dispute is
resolved); provided, however, that such holder shall hold the security deposit
subject to Tenant's rights with respect to the security deposit set forth
herein.

         (c) Tenant shall have the right to deliver to Landlord an
unconditional, irrevocable letter of credit (the "Letter of Credit") in
substitution for the cash security deposit, subject to the following terms and
conditions. Such letter of credit shall be (a) in form and substance
satisfactory to Landlord in its sole discretion; (b) at all times in the amount
of the security deposit, and shall permit multiple draws; (c) issued by a
commercial bank reasonably acceptable to Landlord from time to time and located
in or having a corresponding bank in the Washington, D.C., New York, New York or
Boston, Massachusetts metropolitan area; (d) made payable to, and expressly
transferable and assignable at no charge by, the owner from time to time of the
Building or, at Landlord's option, the holder of any mortgage (which
transfer/assignment shall be conditioned only upon the execution of a written
document in connection therewith); (e) payable at sight upon presentment to a
local branch of the issuer of a simple sight draft or certificate stating that
Tenant is in monetary or other material default under this Lease beyond any
applicable notice and cure period and the amount that Landlord is owed in
connection therewith; (f) of a term not less than one year; and (g) at least
thirty (30) days prior to the then-current expiration date of such letter of
credit, either (1) renewed (or automatically and unconditionally extended) from
time to time through the ninetieth (90th) day after the expiration of the Lease
Term, or (2) replaced with cash in the amount of the Security Deposit.
Notwithstanding anything in this Lease to the contrary, any cure or grace
periods set forth in this Lease shall not apply to Tenant's failure to timely
comply with the requirements of subsection (g) above, in which event Landlord
shall have the right to immediately draw upon the letter of credit without
notice to Tenant and apply the proceeds to the security deposit. Each Letter of
Credit shall be issued by a commercial bank that has a credit rating with
respect to certificates of deposit, short term deposits or commercial paper of
at least P-2 (or equivalent) by Moody's Investor Service, Inc., or at least A-2
(or equivalent) by Standard & Poor's Corporation, and shall be otherwise
acceptable to Landlord in its sole and absolute discretion. If the issuer's
credit rating is reduced below P-2 (or equivalent) by Moody's Investors Service,
Inc. or below A-2 (or equivalent) by Standard & Poor's Corporation, then
Landlord shall have the right the require that Tenant obtain from a different
issuer a substitute letter of credit that complies in all respects with the
requirements of this Section, and Tenant's failure to obtain such substitute
letter of credit within fifteen (15) days following Landlord's written demand
therefor (with no other notice or cure or grace period being applicable thereto,
notwithstanding anything in this Lease to the contrary) shall entitle Landlord
to immediately draw upon the then existing Letter of Credit in whole or in part,
without notice to Tenant. In the event the issuer of any Letter of Credit held
by Landlord is placed into receivership or conservatorship by the Federal
Deposit Insurance


                                       20
<PAGE>   23

Corporation or any successor or similar entity, then, effective as of the date
such receivership or conservatorship occurs, said Letter of Credit shall be
deemed to not meet the requirements of this Section, and, within fifteen (15)
days thereof, Tenant shall replace such Letter of Credit with cash or such other
collateral acceptable to Landlord in its sole and absolute discretion (and
Tenant's failure to do so shall, notwithstanding anything in this Lease to the
contrary, constitute an Event of Default for which there shall be no notice or
grace or cure periods being applicable thereto other than the aforesaid fifteen
(15) day period). Any failure or refusal of the issuer to honor the letter of
credit shall be at Tenant's sole risk and shall not relieve Tenant of its
obligations hereunder with respect to the security deposit.

         (d) Provided that, as of the applicable Reduction Date (as defined
below) no monetary default or any Event of Default shall then be in existence,
Tenant shall have the right with respect to each Reduction Date to reduce the
portion of the security deposit by the amount set forth below with respect to
each Reduction Date (provided, however, that subject to the provisions of this
subsection (d), if any previously existing monetary default is cured within the
applicable notice and cure period and/or any previously existing Event of
Default is thereafter cured by Tenant, then the Reduction Date shall be extended
to the date on which such cure shall have been effected):

<TABLE>
<CAPTION>
                                                                   SECURITY DEPOSIT
               REDUCTION DATE                                      REDUCTION AMOUNT
               --------------                                      ----------------
<S>                                                     <C>
        First day of second Lease Year                  5% of initial letter of credit amount
        First day of third Lease Year                   5% of initial letter of credit amount
        First day of fourth Lease Year                  10% of initial letter of credit amount
        First day of fifth Lease Year                   10% of initial letter of credit amount
        First day of sixth Lease Year                   10% of initial letter of credit amount
        First day of seventh Lease Year                 10% of initial letter of credit amount
        First day of eighth Lease Year                  15% of initial letter of credit amount
        First day of ninth Lease Year                   15% of initial letter of credit amount
        First day of tenth Lease Year                   15% of initial letter of credit amount
</TABLE>

If all of the aforesaid conditions are met, the security deposit shall be so
reduced in accordance with this Section 5.1(d). Notwithstanding anything herein
to the contrary, if there have been more than three (3) Events of Default, then
there shall occur no further reduction in the security deposit. If any portion
of the security deposit is then in the form of a letter of credit, such
reduction shall occur by means of delivery by Tenant to Landlord of a substitute
Letter of Credit or an amendment to the Letter of Credit in such amount and in
strict conformity with the terms of this Article V, in which event, the original
Letter of Credit will be promptly returned to Tenant. For the purposes of this
Lease, the terms "monetary default" and "monetary Events of Default" shall
include any default or Event of Default with respect to Tenant's obligation to
maintain insurance coverage pursuant to the provisions of Article XIII,
provided, however, that in lieu of the notice and cure provision set forth in
Article XIX, with respect to Tenant's failure in its obligation to maintain
insurance coverage, Tenant shall have a period of five (5) days after Tenant
receives written notice, which notice may be delivered by facsimile, of such
failure to cure such failure.


                                       21
<PAGE>   24

     5.2 In the event of the sale or transfer of Landlord's interest in the
Building, Landlord shall transfer the security deposit to the purchaser or
assignee, and provided such transferee assumes Landlord's obligations hereunder
arising from and after the date of the transfer, Tenant shall look only to such
purchaser or assignee for the return of the security deposit, and Landlord,
subject to the provisions of Section 15.6 below, shall thereupon be released
from all liability to Tenant for the return of the security deposit. If the
security deposit is in the form of a letter of credit, then Tenant shall, within
ten (10) days after Landlord's request therefor, have the Letter of Credit
amended or reissued by the issuer to indicate the new beneficiary.

     5.3 Tenant hereby acknowledges that Tenant will not look to the holder of
any mortgage (as defined in Section 21.1) encumbering the Building for return of
the security deposit if such holder, or its successors or assigns, shall succeed
to the ownership of the Building, whether by foreclosure or deed in lieu
thereof, except if and to the extent the security deposit is actually
transferred to such holder.

                                   ARTICLE VI
                                 USE OF PREMISES

     6.1 (a) Tenant shall use and occupy the Premises solely for general office
use and ancillary uses thereto such as training facilities and a computer lab
consistent with the character of the Building and for no other use or purpose.
Tenant shall not use or occupy the Premises for any unlawful purpose or in any
manner that will constitute waste, nuisance or unreasonable annoyance to the
Landlord or other tenants of the Building. Tenant shall comply with all present
and future laws, ordinances (including zoning ordinances and land use
requirements), regulations, and orders of the State of Maryland, the United
States of America and any other public or quasi-public authority having
jurisdiction over the Premises (collectively, "LEGAL REQUIREMENTS"), concerning
the use, occupancy or condition of the Premises and all machinery, equipment and
furnishings therein, including, but not limited to the Americans with
Disabilities Act and regulations promulgated from time to time thereunder.
Landlord shall obtain at Tenant's expense, subject to application of the Tenant
Improvement Allowance, the initial occupancy permit required for Tenant to
lawfully occupy the Premises. If, after Tenant's initial occupancy of the
Premises, any such Legal Requirement requires an occupancy or use permit or
license for the Premises, the operation of the business conducted therein, then
Tenant shall obtain and keep current such permit or license at Tenant's expense
and shall promptly deliver a copy thereof to Landlord. It is expressly
understood that if any change in the use of the Premises by Tenant, or any
alterations to the Premises by Tenant, or any future law, ordinance, regulation
or order requires a new or additional permit from, or approval by, any
governmental agency having jurisdiction over the Building, such permit or
approval shall be obtained by Tenant on its behalf and at its sole expense.
Further, Tenant shall comply with all Legal Requirements which shall impose a
duty on Landlord or Tenant relating to or as a result of the use or occupancy of
the Premises. Tenant shall pay all fines, penalties and damages that may arise
out of or be imposed on Landlord or Tenant because of Tenant's failure to comply
with the provisions of this Lease.

         (b) Subject to Tenant's obligations under Article IV of this Lease,
Landlord shall comply or use commercially reasonable efforts to cause compliance
with all notices it receives of violation of any Legal Requirements that are
applicable to the operation of the


                                       22
<PAGE>   25

common and public areas in the Building and to the machinery and equipment
provided by Landlord in the operation of the Building. Notwithstanding anything
to the contrary in this Section 6.1, all additions, replacements or alterations
to the Building (other than the Premises) which are required due to the
enactment of any future Legal Requirements shall be performed by Landlord and
the cost thereof shall be an Operating Expense (if and to the extent permitted
in accordance with Article IV of this Lease) unless such addition, replacement
or alteration is necessitated by Tenant's particular use, design or layout of
the Premises or caused by the negligence or willful acts or omissions of Tenant
or any of its employees, agents, contractors or subtenants in which case Tenant
shall bear the entire cost of performing such addition, replacement or
alteration

         (c) Tenant shall pay any business, rent or other taxes that are now or
hereafter levied upon Tenant's use or occupancy of the Premises, the conduct of
Tenant's business at the Premises, or Tenant's equipment, fixtures or personal
property. In the event that any such taxes are enacted, changed or altered so
that any of such taxes are levied against Landlord or the mode of collection of
such taxes is changed so that Landlord is responsible for collection or payment
of such taxes, Tenant shall pay any and all such taxes to Landlord upon written
demand from Landlord.

     6.2 (a) Tenant shall not cause or permit any Hazardous Materials (as
defined below) to be generated, used, released, stored or disposed of in or
about the Building, provided that Tenant may use and store in accordance with
all Environmental Laws reasonable quantities of standard cleaning materials as
may be reasonably necessary for Tenant to conduct normal general office use
operations in the Premises. At the expiration or earlier termination of this
Lease, Tenant shall surrender the Premises to Landlord free of Hazardous
Materials and in compliance with all Environmental Laws. "HAZARDOUS MATERIALS"
means (a) asbestos and any asbestos containing material and any substance that
is then defined or listed in, or otherwise classified pursuant to, any
Environmental Law (as defined below) or any other applicable Laws as a
"hazardous substance," "hazardous material," "hazardous waste," "infectious
waste," "toxic substance," "toxic pollutant" or any other formulation intended
to define, list, or classify substances by reason of deleterious properties such
as ignitability, corrosivity, reactivity, carcinogenicity, toxicity,
reproductive toxicity, or Toxicity Characteristic Leaching Procedure (TCLP)
toxicity, (b) any petroleum and drilling fluids, produced waters, and other
wastes associated with the exploration, development or production of crude oil,
natural gas, or geothermal resources, and (c) any petroleum product,
polychlorinated biphenyls, urea formaldehyde, radon gas, radioactive material
(including any source, special nuclear, or byproduct material), medical waste,
chlorofluorocarbon, lead or lead-based product, and any other substance whose
presence could be detrimental to the Building or the Land or hazardous to health
or the environment. "ENVIRONMENTAL LAW" means any present and future law and any
amendments (whether common law, statute, rule, order, regulation or otherwise),
permits and other requirements or guidelines of governmental authorities
applicable to the Building or the Land and relating to the environment and
environmental conditions or to any Hazardous Material (including, without
limitation, CERCLA, 42 U.S.C. Section 9601 et seq., the Resource Conservation
and Recovery Act of 1976, 42 U.S.C. Section 6901 et seq., the Hazardous
Materials Transportation Act, 49 U.S.C. Section 1801 et seq., the Federal Water
Pollution Control Act, 33 U.S.C. Section 1251 et seq., the Clean Air Act, 33
U.S.C. Section 7401 et seq., the Toxic Substances Control Act, 15 U.S.C. Section
2601


                                       23
<PAGE>   26

et seq., the Safe Drinking Water Act, 42 U.S.C. Section 300f et seq., the
Emergency Planning and Community Right-To-Know Act, 42 U.S.C. Section 1101 et
seq., the Occupational Safety and Health Act, 29 U.S.C. Section 651 et seq., and
any so-called "Super Fund" or "Super Lien" law, any Law requiring the filing of
reports and notices relating to hazardous substances, environmental laws
administered by the Environmental Protection Agency, and any similar state and
local laws, all amendments thereto and all regulations, orders, decisions, and
decrees now or hereafter promulgated thereunder concerning the environment,
industrial hygiene or public health or safety). Notwithstanding any termination
of this Lease, Tenant shall indemnify and hold Landlord, its employees and
agents harmless from and against any damage, injury, loss, liability, charge,
demand or claim based on or arising out of the presence or removal of, or
failure to remove, Hazardous Materials generated, used, released, stored or
disposed of by Tenant or any Invitee in or about the Building, whether before or
after Lease Commencement Date. In addition, Tenant shall give Landlord immediate
verbal and follow-up written notice of any actual or threatened Environmental
Default (as defined below), which Environmental Default Tenant shall cure in
accordance with all Environmental Laws and to the satisfaction of Landlord and
only after Tenant has obtained Landlord's prior written consent, which shall not
be unreasonably withheld. An "ENVIRONMENTAL DEFAULT" means any of the following
which is caused by Tenant or any Invitee: a violation of an Environmental Law; a
release, spill or discharge of a Hazardous Material on or from the Premises, the
Land or the Building; an environmental condition requiring responsive action; or
an emergency environmental condition. Upon any Environmental Default, in
addition to all other rights available to Landlord under this Lease, at law or
in equity, Landlord shall have the right but not the obligation to immediately
enter the Premises, to supervise and approve any actions taken by Tenant to
address the Environmental Default, and, if Tenant fails to immediately address
same to Landlord's satisfaction, to perform, at Tenant's sole cost and expense,
any lawful action necessary to address same. If any lender or governmental
agency shall require testing to ascertain whether an Environmental Default is
pending or threatened and such testing indicates an Environmental Default, then
Tenant shall pay the reasonable costs therefor as additional rent. Promptly upon
request, Tenant shall execute from time to time affidavits, representations and
similar documents concerning Tenant's best knowledge and belief regarding the
presence of Hazardous Materials at or in the Building, the Land or the Premises.
Tenant shall not generate, dispose of or maintain any toxic or hazardous
substances in the Premises other than cleaning agents and other substances
normally and customarily used by office tenants and which are not prohibited by
applicable law and which Tenant shall store and shall use in accordance with
applicable law.

         (b) Landlord represents that, except as specified in that certain Phase
I Environmental Site Assessment (the "ENVIRONMENTAL REPORT") prepared by Law
Engineering, dated December 1997 to its actual knowledge as of the date of this
Lease, based solely and exclusively on the Environmental Report and no further
or additional inspection or inquiry having been made, neither the Premises, nor
the Land (collectively, the "Property") contain any Hazardous Materials in
violation of any Environmental Law. Landlord shall not knowingly permit any
Hazardous Materials to be used in the construction or development of the
Property in violation of any Environmental Law. In the event Landlord is
advised, or it shall come to Landlord's attention, that Hazardous Materials
exist in the Premises, if mandated by any Legal Requirement, Landlord shall take
all reasonable steps necessary to promptly remove or abate as required, at
Landlord's expense, all such Hazardous Materials, and in doing so, Landlord
shall


                                       24
<PAGE>   27

use its reasonable efforts not to materially interfere with the conduct of
Tenant's business; provided, however, that Landlord shall remove, at Tenant's
expense, any Hazardous Materials from the Premises which Tenant or its Invitees
shall have introduced or otherwise brought in, on or about the Premises.
Notwithstanding anything herein to the contrary, no holder of any mortgage (nor
any person or entity claiming by, through or under any such holder) shall have
any liability under this Section 6.3(b) or any responsibility to perform any of
Landlord's obligations set forth in this Section 6.3(b); however, any person or
entity claiming by, through or under any such holder and which obtains ownership
of the Property, shall have liability under this Section 6.3(b) and shall be
responsible to perform Landlord's obligation hereunder, but only to the extent
such obligations arise during such period of time as it shall have ownership of
the Property.

                                   ARTICLE VII
                            ASSIGNMENT AND SUBLETTING

     7.1 (a) Except as expressly provided in this Article VII, Tenant shall not
have the right to assign, transfer, mortgage or otherwise encumber this Lease or
its interest herein without first obtaining the prior written consent of
Landlord, which consent may be granted or withheld by Landlord in its sole
discretion. Except as expressly provided in this Article VII, no assignment or
transfer of this Lease or the right of occupancy hereunder may be effectuated by
operation of law or otherwise without the prior written consent of Landlord,
which consent may be granted or withheld by Landlord in its sole discretion
(except as otherwise provided in this Article VII). If Tenant is a partnership,
a withdrawal or change, whether voluntary, involuntary or by operation of law,
of partners owning, individually or collectively, a controlling interest in
Tenant shall be deemed a voluntary assignment of this Lease and shall be subject
to the foregoing provisions. If Tenant is a corporation, any dissolution,
merger, consolidation or other reorganization of Tenant, or the sale or transfer
of a controlling interest of the capital stock of Tenant, shall be deemed a
voluntary assignment of this Lease and subject to the foregoing provisions.
However, the preceding sentence shall not apply to corporations the stock of
which is traded through a national or regional stock exchange. Except as
expressly provided in this Article VII, any attempted assignment or transfer by
Tenant of this Lease or its interest herein without Landlord's consent shall, at
the option of Landlord, constitute an immediate Event of Default under this
Lease, without Landlord having to provide Tenant any notice as may otherwise be
required under Section 19.2 below and Tenant shall remain liable for all rent
and other sums due under this Lease and all damages suffered by Landlord on
account of such breach by Tenant.

         (b) Notwithstanding the restrictions on assignment set forth in Section
7.1(a) above or the provisions of Section 7.3 below, Landlord's prior consent
shall not be required with respect to any assignment of this Lease resulting
from the merger, consolidation, or other corporate reorganization of Tenant, or
the sale or transfer of the capital stock of Tenant, provided that (i) Tenant
after such merger, consolidation, reorganization or sale of stock has a
creditworthiness (e.g. assets and capitalization) and net worth (which shall be
determined on a pro forma basis using generally accepted accounting principles
consistently applied and using the most recent financial statements) at least
equal to or greater than the credit worthiness and net worth of Tenant
immediately prior to such merger, consolidation, reorganization or sale of
stock,


                                       25
<PAGE>   28

(ii) Tenant after such merger, consolidation, reorganization or sale of stock
agrees in writing to be bound by the terms and conditions of this Lease and to
assume all of the obligations and liabilities of Tenant under this Lease, (iii)
Tenant after such merger, consolidation, reorganization or sale of stock shall
conduct substantially the same business on the Premises as that conducted by
Tenant prior thereto or a related business which is a permitted use pursuant to
Article VI of the Lease, (iv) Tenant provides Landlord with prior written notice
of its intent to assign all or a portion of the Premises not more than ninety
(90) nor less than fifteen (15) days prior to the date such assignment is to be
effective, (v) the character of Tenant after the merger, consolidation,
reorganization or sale of stock, as the case may be, and the nature of Tenant's
activities on the Premises and in the Building will not change so as to
adversely affect other tenants in the Building or impair the reputation of the
Building as a first-class office building, (vi) the assignment is not a
so-called "sham" transaction intended by Tenant to circumvent the provisions of
Article VII of the Lease, (vii) Tenant is not in default, beyond any applicable
notice and cure period, under any of the terms and provisions of this Lease and
(viii) the assignment (A) will not result in a material increase in Operating
Expenses for the Building beyond that which Landlord now incurs for use by
Tenant and (B) will not materially increase the burden on elevators or other
Building systems or equipment over the burden prior to such assignment.

         (c) In the event of any such assignment pursuant to Section 7.1(b)
above, Tenant shall remain fully liable as a primary obligor and principal for
Tenant's obligations and responsibilities under this Lease, including without
limitation, the payment of all rent and other charges required hereunder and the
performance of all conditions and obligations to be performed under this Lease.

     7.2 Tenant shall not have the right to sublease (which term, as used
herein, shall include any type of subrental arrangement and any type of license
to occupy) all or any part of the Premises without first obtaining the prior
written consent of Landlord, which consent shall not be unreasonably withheld,
conditioned or delayed; provided, however, that it shall not be unreasonable for
Landlord to withhold its consent if Tenant is in monetary or other material
non-monetary default beyond any applicable notice and cure provision under this
Lease, or if Landlord determines, in its reasonable discretion, that the
character of the proposed subtenant or the nature of the activities to be
conducted by such proposed subtenant would materially adversely affect the other
tenants of the Building or would impair the reputation of the Building as a
first-class office building, or that the character of the business to be
conducted or the proposed use of the Premises by the proposed subtenant or
assignee (i) is likely to increase in a material respect the Operating Expenses
for the Building beyond that which Landlord now incurs for use of by Tenant;
(ii) is likely to increase in a material respect the burden on elevators or
other Building systems or equipment over the burden prior to such proposed
subletting or assignment; (iii) violates or is likely to violate any provisions
or restrictions contained herein relating to the use or occupancy of the
Premises; or (iv) the proposed sublease may have an adverse effect on the real
estate investment trust qualification tests applicable to Landlord and its
affiliates. Any attempted subletting by Tenant of any portion of the Premises
without Landlord's consent if and to the extent required, shall, at the option
of Landlord, constitute an immediate Event of Default under this Lease, without
Landlord having to provide Tenant any notice as may otherwise be required under
Section 19.2 below and Tenant shall remain liable for all rent and other sums
due under this Lease and all damages suffered by Landlord on account of such
breach


                                       26
<PAGE>   29

by Tenant. Furthermore, except as otherwise provided in this Article VII, Tenant
shall not have the right to sublease all or any portion of the Premises without
first complying with the provisions of subsections (a) through (e) below:

         (a) Tenant shall give Landlord written notice of its desire to sublease
all or a portion of the Premises. Such notice shall specify the portion of the
Premises proposed to be sublet and the date such portion is to be made available
for subleasing. If Tenant subleases or as a result of such sublease, would in
the aggregate be subleasing fifty percent (50%) or more of the rentable area in
the original Premises, Landlord shall have the right to retake possession of the
portion of the Premises proposed to be sublet. If Tenant subleases, or as a
result of such sublease, would in the aggregate sublease less than fifty percent
(50%) of the rentable area in the original Premises, Landlord shall not have the
right to retake possession of the portion of the Premises proposed to be sublet.
If, subject to the terms of this Section 7.2(a), Landlord has the right to
retake possession of the portion of the Premises proposed to be sublet, within
fifteen (15) days after receipt of such notice, Landlord shall notify tenant in
writing whether or not Landlord will retake possession of the portion of the
Premises proposed to be sublet and thereby delete such portion of the Premises
from the Premises being leased to Tenant hereunder. If Landlord elects to retake
such portion of the Premises, (i) Landlord shall retake possession of such
portion on the date specified in Tenant's notice, (ii) Tenant's obligation to
pay base rent and additional rent attributable to increases in Operating
Expenses for such recaptured portion of the Premises shall cease on such date
and the security deposit provided in accordance with Article V hereof shall be
reduced proportionately and (iii) Landlord and Tenant shall promptly execute an
amendment to the Lease setting forth the new square footage of the reduced
premises to be occupied by Tenant. Thereafter, Tenant shall not have any further
rights of any kind, including any right of renewal, in or to the portion of the
Premises so retaken. If Landlord does not elect to retake such portion of the
Premises within the aforesaid fifteen (15) day period, Tenant shall comply with
the provisions of subsections (b) and (c) below with respect to any proposed
sublease of such portion of the Premises.

         (b) Notwithstanding anything to the contrary in this Article VII,
Tenant shall in no event have the right to sublease the Premises, or any portion
thereof, to more than three (3) subtenants at any one time on any floor of the
Premises without Landlord's prior written approval.

         (c) Tenant agrees to give Landlord at least fifteen (15) days advance
written notice of Tenant's intention to sublease a portion of the Premises to a
particular subtenant, along with sufficient information about the proposed
subtenant to enable Landlord to make the determination called for by subsection
(b) above. Landlord agrees to advise Tenant of its decision to grant or withhold
its consent to such subletting within fifteen (15) business days after
Landlord's receipt of such notice by Tenant. Landlord shall use reasonable
efforts to obtain all required third party approvals, if any, within such
fifteen (15) business day period.

         (d) Tenant's right to sublease any portion of the Premises that
Landlord does not have the right to recapture or that Landlord has not elected
to retake pursuant to subsection (a) above shall expire one hundred eighty (180)
days after the giving of the notice required by subsection (a). Thereafter,
Tenant shall have no right to sublease the portion of the Premises


                                       27
<PAGE>   30

described in the notice furnished pursuant to subsection (a), unless Tenant
shall have again complied with the procedures set forth in this Section 7.2.
Notwithstanding anything to the contrary in this Section 7.2(d), in the event
Tenant's ongoing and continuing negotiations with one (1) prospective subtenant
shall extend beyond such one hundred eighty (180) day period, Tenant shall not
be obligated to repeat the procedures set forth in this Section 7.2 for an
additional period of ninety (90) days, provided that Tenant shall provide
Landlord with written notice that its negotiations with such prospective
subtenant are continuing. In the event Tenant's negotiations with such
prospective subtenant fail after the expiration of such additional ninety (90)
day period, Tenant shall have no right to sublease the portion of the Premises
described in the notice furnished pursuant to subsection (a) and subsection (d)
above, to another prospective subtenant, unless Tenant shall have again complied
with the procedures set forth in this Section 7.2.

         (e) Provided (i) there is not an ongoing monetary or other material
non-monetary default under any terms and provisions of this Lease, beyond any
applicable notice and cure period and (y) Tenant subleases no more than the
number of rentable square feet comprising one (1) full floor of the Premises,
Tenant shall be entitled to retain one hundred percent (100%) of any profit
derived from subletting the Premises or any part thereof. Provided (x) there is
not an ongoing monetary or other material non-monetary default under any terms
and provisions of this Lease beyond any applicable notice and cure period and
(y) Tenant subleases more than the number of rentable square feet comprising one
(1) full floor of the Premises, Tenant shall be entitled to retain one hundred
percent (100%) of any profit derived from subletting up to the number of
rentable square feet comprising one (1) full floor of the Premises and Landlord
and Tenant shall share equally (i.e. fifty percent (50%) each) in any profit
derived from Tenant's subletting more than the number of rentable square feet
comprising one (1) full floor of the Premises or any part thereof. Landlord,
upon reasonable prior written notice to Tenant, shall have the right to inspect
and audit Tenant's books and records relating to any sublease or assignment and
expenses incurred by Tenant in connection therewith. Upon Landlord advising
Tenant of any potential adverse effect of any proposed sublease or assignment on
the real estate investment trust qualification tests applicable to Landlord and
its affiliates, which advice shall be made at or before the time Landlord
provides Tenant with its approval of a sublease or assignment, Tenant will
exercise its commercially reasonable efforts to structure any such proposed
sublease or assignment so that the portion of the excess rents that become
payable to Landlord will not have such adverse effect, and if Tenant is unable
so to structure any proposed sublease or assignment, then Landlord shall have
the right in its sole and absolute discretion to withhold its consent to the
proposed sublease. For the purposes of this Section 7.2(e), Tenant's profit
shall be calculated after taking into account Tenant's actual, out-of-pocket
costs expenses incurred in connection with a sublease, including, without
limitation, any free rent, improvement or moving allowance provided to the
applicable subtenant, brokerage costs and reasonable attorneys' fees.

         (f) Landlord acknowledges that Tenant intends to sublease (the "NOS
Sublease") a portion of the Premises (the "NOS Space") to National Operator
Services, Inc. ("NOS"). Landlord hereby consents to the NOS Sublease. Landlord
agrees that for so long as (i) NOS is owned or controlled by Richard Kay and/or
his immediate family members and (ii) the NOS Space comprises is no more than
10,000 square feet of rentable area in the Premises.


                                       28
<PAGE>   31

Notwithstanding anything herein to the contrary, Landlord shall not have the
right to approve NOS's sublease of the NOS Space, nor shall Landlord have the
right to recapture the NOS Space and Landlord shall include the NOS Space as a
part of the Premises when making the square footage determination called for in
this Lease.

     7.3 Notwithstanding the provisions of Section 7.1(a), 7.2 or 7.5(a) hereof
to the contrary, if consent to any assignment or subletting is required by the
holder of any mortgage on the Building, no assignment of this Lease or sublease
of all or any portions of the Premises shall be permitted without the prior
written consent of such holder. Landlord agrees to use its reasonable efforts to
obtain promptly such required consent to any proposed subletting or assignment.
The grounds for any future holder of a mortgage secured by the Building to
withhold its consent to a proposed assignment of this Lease or sublease of all
or any portion of the Premises shall be limited to those bases specifically
enumerated in this Article VII. Subleases of not more than one (1) full floor of
the Building for a term three (3) years or less shall not require the consent of
Landlord's lender. If any future holder of a mortgage secured by the Building
fails to respond within fifteen (15) business days to a request for its consent
to any assignment or subletting hereunder, such future mortgage holder's consent
to such assignment or sublease in that particular instance shall be deemed to
have been granted.

     7.4 The consent by Landlord to any assignment or subletting shall not be
construed as a waiver or release of Tenant from any and all liability for the
performance of all covenants and obligations to be performed by Tenant under
this Lease, nor shall the collection or acceptance of rent from any assignee,
transferee or subtenant constitute a waiver or release of Tenant from any of its
liabilities or obligations under this Lease. Landlord's consent to any
assignment or subletting shall not be construed as relieving Tenant from the
obligation of complying with the provisions of Sections 7.1 or 7.2 hereof, as
applicable, with respect to any subsequent assignment or subletting. For so long
as Tenant is in monetary or other non-monetary material default under this Lease
beyond any applicable notice and cure provision, Tenant hereby assigns to
Landlord the rent due from any subtenant of Tenant and hereby authorizes each
subtenant to pay said rent directly to Landlord. To the extent Landlord's
consent or approval is required in accordance with the provisions of this
Article VII, Tenant further agrees to submit any and all instruments of
assignment and sublease to Landlord for Landlord's prior written approval as to
form and substance, which approval shall not be unreasonably withheld,
conditioned or delayed, but which instruments shall provide, as an express
condition precedent to Landlord's prior approval, that any assignee agree to
remain jointly and severally liable to Landlord for all obligations imposed by
any such agreement of assignment. Landlord hereby approves the form of sublease
attached hereto as Exhibit G and agrees to approve subleases that are submitted
to it in substantially the form attached hereto as Exhibit G.

     7.5 (a) Notwithstanding anything in this Article VII to the contrary,
Landlord's prior consent shall not be required with respect to any assignment or
subletting to an "Affiliate of Tenant" (as hereinafter defined) or a "Parent of
Tenant" (as hereinafter defined), provided (i) that such assignee has a
creditworthiness (e.g. assets and capitalization) and net worth (which shall be
determined on a pro forma basis using generally accepted accounting principles
consistently applied and using the most recent financial statements) at least
equal to or greater than the credit worthiness and net worth of Tenant
immediately prior to such assignment, (ii) that such assignee


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<PAGE>   32

agrees in writing to be bound by the terms and conditions of this Lease and to
assume all of the obligations and liabilities of Tenant under this Lease or that
such sublessee executes a sublease in the form attached hereto as Exhibit H,
(iii) that such assignee or sublessee shall conduct a business on the Premises
which is a permitted use pursuant to Article VI of this Lease, (iv) that Tenant
provides Landlord with prior written notice of its intent to assign or sublease
all or a portion of the Premises not more than ninety (90) nor less than fifteen
(15) days prior to the date such assignee or sublessee is to occupy the
Premises, (v) that the character of such person or entity and the nature of its
activities on the Premises and in the Building will not adversely affect other
tenants in the Building or impair the reputation of the Building as a
first-class office building, and (vi) that the sublease with such person or
entity is not a so-called "sham" transaction intended by Tenant to circumvent
the provisions of this Article VII.

         (b) In the event of any such assignment or subletting pursuant to this
Section 7.5, Tenant shall remain fully liable as a primary obligor and principal
for Tenant's obligations and responsibilities under this Lease, including
without limitation, the payment of all rent and other charges required hereunder
and the performance of all conditions and obligations to be performed under this
Lease.

         (c) For purposes of this Section 7.5, an "Affiliate of Tenant" shall
mean any corporation, association, trust or partnership (i) which Controls (as
herein defined) Tenant or (ii) which is under the Control of Tenant through
stock ownership or otherwise or (iii) which is under common Control with Tenant.
For the purposes hereof, a "Parent of Tenant" shall mean any corporation,
association, trust or partnership (i) which Controls Tenant or (ii) which owns
more than fifty percent (50%) of the issued and outstanding voting securities of
Tenant. The terms "Control" or "Controls" as used in this Section 7.5 shall mean
the power directly or indirectly to influence the direction, management or
policies of Tenant or such other entity.

     7.6 No part of the rent payable under this Lease shall be based in whole or
in on the income or profits derived from the Premises except for percentage rent
based on gross (not net) receipts or sales part. If the lender providing
financing for all or any portion of the Project succeeds to Landlord's interests
under this Lease and such lender's counsel advises Landlord that all or any
portion of the rent payable under this Lease is or may be deemed to be unrelated
business income within the meaning of the Internal Revenue Code or regulations
issued thereunder, such lender may elect to amend unilaterally the calculation
of rent so that none of the rent payable to such lender under this Lease will
constitute unrelated business income but the amendment shall not increase
Tenant's payment obligations or other liability under this Lease or reduce
Landlord's obligations under this Lease. At such lender's request, Tenant shall
execute any document such lender deems necessary to effect such amendment of
this Lease. Any sublease of all or any portion of the Premises shall include the
foregoing provisions of this Section 7.6.

                                  ARTICLE VIII
                        TENANT'S MAINTENANCE AND REPAIRS

     8.1 Tenant will keep and maintain the interior, non-structural portions of
the Premises and all fixtures and equipment (other than base Building equipment
and systems) located therein


                                       30
<PAGE>   33

in clean, safe and sanitary condition, will take good care thereof and make all
required repairs thereto, and will suffer no waste or injury thereto. At the
expiration or other termination of the Lease Term, Tenant shall surrender the
Premises, broom clean, in the same order and condition in which they are in on
the Lease Commencement Date, ordinary wear and tear and unavoidable damage by
the elements excepted.

     8.2 Except as otherwise provided in Article XVII hereof and subject to the
provisions of Section 13.4 below, all injury, breakage and damage to the
Premises and to any other part of the Building caused by any act or omission of
Tenant, or of any agent, employee, subtenant, contractor or customer ("INVITEE")
of Tenant, shall be repaired by and at the sole expense of Tenant, except that
Landlord shall have the right, at its option, to make such repairs and to charge
Tenant for all reasonable costs and expenses incurred in connection therewith as
additional rent hereunder. The liability of Tenant for such costs and expenses
shall be reduced by the amount of any insurance proceeds received by Landlord on
account of such injury, breakage or damage.

     8.3 Landlord shall keep and maintain the exterior and demising walls,
foundations, roof and common areas that form a part of the Building, including,
without limitation, the Shower Facility, and the base Building standard
mechanical, electrical, HVAC, fire and life safety and plumbing systems, pipes
and conduits that are provided by Landlord in the operation of the Building or,
on a non-exclusive basis, the Premises in clean, safe, sanitary and operating
condition in accordance with standards customarily maintained by first-class
office buildings in the City of Rockville, Montgomery County, Maryland area, and
will make all required repairs and replacements thereto. All common or public
areas of the Building and the land upon which it is situated (including without
limitation the first floor and lower level lobby area and the exterior
landscaping, including sidewalks and brick pavers) shall be maintained by
Landlord in accordance with standards customarily maintained by first-class
office buildings in the City of Rockville, Montgomery County, Maryland area.
Tenant shall promptly provide Landlord with written notice of any defect or need
for repairs in or about the Building of which Tenant is aware; provided,
however, Landlord's obligation to repair hereunder shall not be limited to
matters of which it has been given notice by Tenant. Notwithstanding any of the
foregoing to the contrary: (a) maintenance and repair of special tenant areas,
facilities, finishes and equipment (including, but not limited to, any special
fire protection equipment, telecommunications and computer equipment,
kitchen/galley equipment, air-conditioning equipment serving the Premises only
and all other furniture, furnishings and equipment of Tenant and all
Alterations) shall be the sole responsibility of Tenant and shall be deemed not
to be a part of the Building structure and systems; and (b) Landlord shall have
no obligation to make any repairs to the Premises brought about by any act or
neglect of Tenant or any Invitee; provided, however that subject to the
provisions of this Article VIII and Article XIII, Landlord, at Tenant's expense,
shall make repairs to Building systems serving the Premises that are brought
about by the act or neglect of Tenant or any Invitee. Landlord shall provide and
install (subject to reimbursement in accordance with Article IV) replacement
tubes and bulbs for Building standard light fixtures in the Premises, if any;
all other bulbs and tubes for the Premises shall be Tenant's responsibility,
however, at Tenant's request, Landlord shall stock and install such other bulbs
and tubes and Tenant shall reimburse Landlord for its cost and expenses incurred
in connection with said stocking and installation.


                                       31
<PAGE>   34

                                   ARTICLE IX
                               TENANT ALTERATIONS

     9.1 The initial improvements in the Premises shall be constructed in
accordance with Exhibit B attached hereto and made a part hereof. It is
understood and agreed that except as provided in the preceding sentence,
Landlord will not make, and is under no obligation to make, any structural or
other alterations, decorations, additions or improvements in or to the Premises.

     9.2 Tenant will not make or permit anyone to make any alterations,
decorations, additions or improvements (hereinafter referred to collectively as
"IMPROVEMENTS" or "ALTERATIONS"), structural or otherwise, in or to the Premises
or the Building, without the prior written consent of Landlord which may be
granted or withheld in Landlord's sole and absolute discretion provided,
however, that Landlord's consent with respect to improvements to the interior of
the Premises which (i) are not readily visible to the exterior of the Building
or the common and public areas thereof, (ii) are not structural, (iii) do not
affect the electrical, mechanical, fire or life safety systems within the
Building and (iv) are otherwise in conformance with all applicable building,
zoning and other codes or regulations affecting the Building, shall not be
unreasonably withheld, conditioned or delayed. Notwithstanding the foregoing,
provided Tenant gives Landlord prior written notice, Tenant may install in the
Premises, without obtaining Landlord's prior written consent, minor,
nonstructural Alterations of a decorative nature and which do not require a
building permit, for example, the hanging of artwork, the painting or covering
of walls or the installation of carpeting ("Aesthetic Alterations") whose value
is less than Fifty Thousand Dollars ($50,000) per Aesthetic Alteration and, when
aggregated with other Aesthetic Alterations in a twelve (12) month period are
less than One Hundred Thousand Dollars ($100,000.00). Structural Alterations
shall be deemed to include without limitation any Alterations that will or may
necessitate any changes, replacements or additions to walls, ceilings,
partitions (other than non-structural or free-standing partitions), columns, or
floors or to the water, electrical, mechanical, plumbing, fire and life safety
or HVAC systems of the Premises or the Building or any Alteration that will
require the issuance of a building permit. Any Alterations made by Tenant shall
be made: (a) in a good, workmanlike, first-class and prompt manner; (b) using
new materials only; (c) by a contractor reasonably approved by Landlord and on
days, at times and, when appropriate under the circumstances, under the
supervision of an architect approved in writing by Landlord; (d) in accordance
with plans and specifications prepared by an engineer or architect reasonably
acceptable to Landlord, which plans and specifications shall be approved in
writing by Landlord (Tenant hereby agreeing to reimburse Landlord for the
reasonable, out-of-pocket costs and expenses incurred in connection with
Landlord's review of the same, if any); (e) in accordance with all laws and the
requirements of any insurance company insuring the Building or any portion
thereof; (f) after having obtained any required consent of the holder of any
Mortgage (Landlord hereby agreeing to use reasonable efforts to obtain such
consent) or such consent being deemed to have been granted; (g) after obtaining
public liability and worker's compensation insurance policies approved in
writing by Landlord, which policies shall cover every person who will perform
any work with respect to such Alteration; (h) on the condition that Tenant shall
obtain and deliver to Landlord not more than ten (10) days after any payment is
to be made, without regard to any dispute between Tenant and its contractors,
subcontractors, laborers and material suppliers, written, unconditional waivers
of mechanics' and materialmen's liens against the Premises and the Building from
all


                                       32
<PAGE>   35

proposed contractors, subcontractors, laborers and material suppliers for all
work, labor and services to be performed and materials to be furnished in
connection with Alterations; and (i) upon request, after Tenant has delivered to
Landlord documentation reasonably satisfactory to Landlord evidencing Tenant's
financial ability to complete the Alteration in accordance with the provisions
of this Lease. If any lien (or a petition to establish such lien) is filed in
connection with any Alteration, such lien (or petition) shall be discharged by
Tenant within fifteen (15) days thereafter, at Tenant's sole cost and expense,
by the payment thereof or by the filing of a bond reasonably acceptable to
Landlord. If Landlord gives its consent to the making of any Alteration, such
consent shall not be deemed to be an agreement or consent by Landlord to subject
its interest in the Premises or the Building to any liens which may be filed in
connection therewith. All Alterations (including, without limitation, those
involving structural, electrical, mechanical or plumbing work, the heating,
ventilation and air conditioning system of the Premises or the Building, and the
roof of the Building, but excluding Aesthetic Alterations) shall, at Landlord's
election, be performed by Landlord's designated contractor or subcontractor at
Tenant's expense; provided, however, that Landlord shall obtain competitive
rates therefor. Promptly after the completion of an Alteration, Tenant at its
expense shall deliver to Landlord three (3) sets of accurate as-built drawings
on CADD computer disc showing such Alteration in place. When granting its
consent, Landlord may impose any conditions it deems appropriate, including,
without limitation, the approval of plans and specifications, approval of the
contractor or other persons who will perform the work, and the obtaining of
required permits and specified insurance. It shall be reasonable for Landlord to
insist that portions of the Premises visible to the public shall maintain a
uniform appearance with the rest of the Building. All improvements permitted by
Landlord must conform to all rules and regulations established from time to time
by the Underwriters' Association of the State of Maryland and to all laws,
regulations and requirements of the Federal, state and local governments.
Landlord's review and approval of any such plans and specifications and its
consent to perform work described therein shall not be deemed an agreement by
Landlord that such plans, specifications and work conform with all applicable
Legal Requirements and requirements of the insurers of the Building ("INSURANCE
REQUIREMENTS") nor deemed a waiver of Tenant's obligations under this Lease with
respect to all applicable Legal Requirements and Insurance Requirements nor
impose any liability or obligation upon Landlord with respect to the
completeness, design sufficiency or compliance with all applicable Legal
Requirements or Insurance Requirements of such plans, specifications and work.
If Tenant shall fail to discharge any such mechanic's or materialmen's lien
within the fifteen (15) day period provided for above, Landlord may, at its
option, discharge such lien and treat the cost thereof (including reasonable
attorneys' fees incurred in connection therewith) as additional rent payable
with the next monthly installment of annual base rent falling due; it being
expressly agreed that such discharge by Landlord shall not be deemed to waive or
release the default of Tenant in not discharging such lien. It is understood and
agreed that any improvements to the Premises shall be conducted on behalf of
Tenant and not on behalf of Landlord, and that Tenant shall be deemed the
"owner" of such improvements (and not the agent of Landlord).

     9.3 Tenant shall indemnify and hold Landlord harmless from and against any
and all expenses, liens, claims, liabilities and damages based on or arising,
directly or indirectly, by reason of the making of any improvements to the
Premises by Tenant, or its contractors, agents or employees. Except for
improvements that do not require Landlord's consent pursuant to


                                       33
<PAGE>   36

Section 9.2 above and subject to the notice and cure provisions of Section
19.1(b) below, if any improvements are made without the prior written consent of
Landlord, Landlord shall have the right to remove and correct such improvements
and restore the Premises to their condition immediately prior thereto, and
Tenant shall be liable for all expenses incurred by Landlord in connection
therewith. All improvements to the Premises or the Building made by either party
shall remain upon and be surrendered with the Premises as a part thereof at the
end of the Lease Term unless (i) Tenant requests, when it submits its plans and
specifications for such improvements to Landlord for Landlord's approval,
Landlord's consent to Tenant's removal of such improvements upon the expiration
or earlier termination of the Lease Term and Landlord so consents or (ii)
Landlord specifies in its approval of the plans and specifications for such
improvements that Tenant must remove the improvements upon the expiration or
earlier termination of the Lease Term, except that if Tenant is not in monetary
or other non-monetary material default under this Lease beyond any applicable
notice and cure period, Tenant shall have the right to remove, prior to the
expiration of the Lease Term, all movable furniture, furnishings and equipment
installed in the Premises solely at the expense of Tenant. The preceding
sentence notwithstanding, Tenant shall be obligated to replace, to Landlord's
sole satisfaction, prior to the expiration of the Lease Term the portion of any
floor/ceiling slab that is removed from the structure of the Building in
connection with the construction and installation of interior stairs in the
Premises. All damages and injury to the Premises or the Building caused by such
removal shall be repaired by Tenant, at Tenant's sole expense. If such property
of Tenant is not removed by Tenant prior to the expiration or termination of
this Lease, the same shall become the property of Landlord and shall be
surrendered with the Premises as a part thereof.

                                    ARTICLE X
                              SIGNS AND FURNISHINGS

     10.1 No sign, advertisement or notice referring to Tenant shall be
inscribed, painted, affixed or otherwise displayed on any part of the exterior
or the interior of the Building except on the directories, elevator lobbies to
which no other tenant has access (i.e. those elevator lobbies located on full
floors leased by Tenant or located in an area to which access is not possible
without going through the Premises) (the "Private Elevator Lobbies") and doors
of offices and such other areas as are designated by Landlord, and then only in
such place, number, size, color and style as are approved by Landlord and are in
accordance with any applicable state or local building code or zoning
regulations and any applicable association rules and regulations.
Notwithstanding anything herein to the contrary, Landlord's consent shall not be
required with respect to any such signage proposed by Tenant that is to be
located within the Private Elevator Lobbies or within the Premises provided such
signage is not visible to the exterior of the Building or the common areas of
the Building. All of Tenant's signs that are approved by Landlord shall, at
Landlord's election, be installed by Landlord at Tenant's cost and expense and
shall be removed by Tenant at Tenant's sole cost and expense at the end of the
Term (and Tenant shall repair any damage to the Building or the Premises caused
by such removal). If any sign, advertisement or notice that has not been
approved by Landlord is exhibited or installed by Tenant, Landlord, subject to
the notice and cure provisions of Section 19.1(b), shall have the right to
remove the same at Tenant's expense. Landlord shall, at its cost, list Tenant's
name in the Building lobby directories up to a maximum number of lines on the
directory equal to one (1)


                                       34
<PAGE>   37

line for each 2,000 square feet of rentable area in the Premises; provided,
however, that if Tenant requests Landlord to change the names on such
directories, then Tenant shall reimburse Landlord for all reasonable,
out-of-pocket costs incurred by Landlord therefor. Landlord's acceptance of any
name for listing on the Building directories will not be deemed, nor will it
substitute for, Landlord's consent, as required by this Lease, to any sublease,
assignment or other occupancy of the Premises. Landlord shall have the right to
prohibit any advertisement of or by Tenant (other than an element of a
nationwide program of advertising) which in its opinion tends to impair the
reputation of the Building or its desirability as a first-class office building
(it being agreed that advertising Tenant's permitted use of the Premises shall
not itself violate the provision of this sentence), and upon notice from
Landlord, Tenant shall immediately refrain from and discontinue any such
advertisement. Subject to the provisions of Section 10.2(a) below, Landlord
reserves the right to affix, install and display signs, advertisements and
notices on any part of the exterior or interior of the Building but not in the
Premises except as maybe required by law or in emergency situations.

     10.2 (a) Subject to the terms and conditions set forth in this Section
10.2, Landlord agrees that Tenant may erect, at Tenant's sole cost and expense,
two (2) signs identifying Tenant and its logo ("Tenant's Signs") on the exterior
walls at the top of the Building; provided, however, that the color, size,
style, location, placement, method of installation and illumination, material
finish and configuration of Tenant's Signs (A) shall be subject to Landlord's
prior written approval, which approval may be granted or withheld by Landlord in
its sole but reasonable discretion, (B) shall comply with all applicable Legal
Requirements, (C) shall be subject to any required Approvals, as defined below
and (D) may be limited or reduced in size but not in number by Landlord based on
Tenant's pro rata share of all of the signage that is allocable to tenants in
the Building who have signage rights based on the number of rentable square feet
in the Building in relation to the number of rentable square feet in the entire
Complex. Landlord agrees that it shall use commercially reasonable efforts to
maximize the signage allowed in the Complex. Tenant's right to signage on the
Building shall be exclusive with respect to the parapet/roof screen level only.
Except as expressly limited in the preceding sentence, Landlord shall have the
right to provide Building signage to other tenants in the Building on other
areas on or around the second (2nd) floor or below of the Building. Tenant shall
be responsible for obtaining and securing, at Tenant's expense, all necessary
permits, approvals or variances with respect to Tenant's Sign from any
applicable federal, state, county, city or other local governing authorities
having jurisdiction over the Building and the Complex (collectively, the
"Approvals"). Landlord, at Tenant's request and expense, shall cooperate with
Tenant in securing any necessary Approvals for Tenant's Sign. In the event
Tenant is unable to obtain the necessary Approvals from any applicable federal,
state, county or other local governing authorities having jurisdiction over the
Building and the Complex, Tenant shall have the right to revise Tenant's Sign in
whatever manner is required to comply with the applicable Approvals, provided
such revisions shall be subject to the prior written approval of Landlord, which
approval shall not be unreasonably withheld, conditioned or delayed and if
Landlord approves such revisions, in the event that Tenant is unable to secure
the required Approvals for the revised Tenant's Sign, Tenant shall have no
remedy, claim, cause of action or recourse against Landlord, nor shall failure
or inability to obtain any necessary Approvals provide or afford Tenant the
opportunity to terminate this Lease. Tenant, at Tenant's sole cost and expense,
shall keep and maintain Tenant's Sign in good condition and repair. Upon the
expiration or earlier termination


                                       35
<PAGE>   38

of this Lease or upon the occurrence of any of the events enumerated in
subsection (c) below, Tenant shall remove, at Tenant's sole cost and expense,
Tenant's Sign from the Building and shall cause, at Tenant's expense, the
surface of the Building to be repaired and returned substantially the same
condition it was in prior to Tenant's Sign being affixed thereto, reasonable
wear and tear and damage by the elements excepted.

         (b) Tenant's rights under this 10.2 are personal to and may be
exercised only by OTG Software, Inc. and shall not be exercisable by any
assignee or subtenant of OTG Software, Inc. other than an assignee permitted or
approved in accordance with the provisions of Article VII above.

         (c) Tenant shall not be entitled to the exclusive signage rights set
forth in this Section 10.2 for so long as Tenant is in monetary or other
non-monetary material default under any of the terms and provisions of this
Lease, beyond any applicable notice and cure period or if, at any time during
the Lease Term Tenant is occupying less than fifty percent (50%) of the original
Premises, as defined in Section 1.1 above.

         (d) Subject to the terms and conditions set forth in this Section
10.2(d), promptly after the execution and delivery of this Lease and all amounts
then due hereunder by Tenant to Landlord, Landlord agrees that Tenant may erect,
at Tenant's sole cost and expense, one (1) sign identifying Tenant and its logo
("Tenant's Temporary Sign") on the Tompkins Construction Company's ("Tompkins")
construction trailer or on the structure of the Building; provided, however,
that the color, size, style, location, placement, method of installation and
illumination, material finish and configuration of Tenant's Temporary Sign (A)
shall be subject to Landlord's and Tompkins' (if Tenant's Temporary Sign is
located on the Tompkins Trailer) prior written approval, which approval may be
granted or withheld by Landlord or Tompkins, as applicable, in its sole but
reasonable discretion, (B) shall comply with all applicable Legal Requirements
and (C) shall be subject to any required Approvals, as defined below. Tenant
shall be responsible for obtaining and securing, at Tenant's expense, all
necessary permits, approvals or variances with respect to Tenant's Temporary
Sign from any applicable federal, state, county, city or other local governing
authorities having jurisdiction over the Building and the Complex (collectively,
the "Approvals"). Landlord, at Tenant's request and expense, shall cooperate
with Tenant in securing any necessary Approvals for Tenant's Temporary Sign. In
the event Tenant is unable to obtain the necessary Approvals from any applicable
federal, state, county or other local governing authorities having jurisdiction
over the Building and the Complex, Tenant shall have the right to revise
Tenant's Temporary Sign in whatever manner is required to comply with the
applicable Approvals, provided such revisions shall be subject to the prior
written approval of Landlord and Tompkins, which approval shall not be
unreasonably withheld, conditioned or delayed and if Landlord approves such
revisions, in the event that Tenant is unable to secure the required Approvals
for the revised Tenant's Temporary Sign, Tenant shall have no remedy, claim,
cause of action or recourse against Landlord or Tompkins, nor shall failure or
inability to obtain any necessary Approvals provide or afford Tenant the
opportunity to terminate this Lease. Tenant, at Tenant's sole cost and expense,
shall keep and maintain Tenant's Temporary Sign in good condition and repair.
Upon the removal by Tompkins of its trailer from the job site, Tenant's
Temporary Sign shall be removed, at Tenant's sole cost and expense, from the
Tompkins


                                       36
<PAGE>   39

trailer (and relocated to the structure of the Building) and the surface of the
Tompkins trailer or the Building, as applicable, at Tenant's expense, shall be
repaired and returned substantially the same condition it was in prior to
Tenant's Temporary Sign being affixed thereto, reasonable wear and tear and
damage by the elements excepted.

     10.3 Landlord shall have the right to prescribe the weight and position of
safes and other heavy equipment and fixtures, which, if considered necessary by
the Landlord in its reasonable judgment, shall be installed in such manner as
Landlord directs in order to distribute their weight adequately. Any and all
damage or injury to the Premises or the Building caused by moving the property
of Tenant into or out of the Premises, or due to the same being in or upon the
Premises, shall be repaired at the sole cost of Tenant. No furniture, equipment
or other bulky matter of any description will be received into the Building or
carried in the elevators except as reasonably approved by Landlord, and all such
furniture, equipment and other bulky matter shall be delivered only through the
designated delivery entrance of the Building and the designated freight
elevator. All moving of furniture, equipment and other materials shall be under
the supervision of Landlord, who shall not, however, be responsible for any
damage to or charges for moving the same. Tenant agrees to remove promptly from
the sidewalks adjacent to the Building any of Tenant's furniture, equipment or
other material there delivered or deposited.

                                   ARTICLE XI
                               TENANT' S EQUIPMENT

     11.1 After the initial installation of Tenant's equipment and machinery in
the Premises in accordance with plans approved by Landlord in accordance with
the provisions of Exhibit B, Tenant will not install or operate in the Premises
any electrically operated equipment or machinery that operates on greater than
110 volt power or exceeds normal electrical usage without first obtaining the
prior written consent of Landlord, which consent shall not be unreasonably
withheld, conditioned or delayed; provided, however, it shall not be
unreasonable for Landlord to condition such consent upon (a) the payment by
Tenant of additional rent in compensation for the excess consumption of
electricity or other utilities and for the cost of any additional wiring or
apparatus that may be occasioned by the operation of such equipment or machinery
and/or (b) the non-interruption or non-disturbance of any other tenant in the
Office Complex that may be occasioned by the operation of such equipment or
machinery. Landlord may condition such consent upon the payment by Tenant of
additional rent in compensation for the excess consumption of electricity or
other utilities and for the cost of any additional wiring or apparatus that may
be occasioned by the operation of such equipment or machinery. Tenant shall not
install any equipment of any type or nature that will or may necessitate any
changes, replacements or additions to, or in the use of, the water system,
heating system, plumbing system, air-conditioning system or electrical system of
the Premises or the Building, without first obtaining the prior written consent
of Landlord. Business machines and mechanical equipment belonging to Tenant
which cause noise or vibration that may be transmitted to the structure of the
Building or to any space therein to such a degree as to be objectionable to
Landlord or to any tenant in the Building shall be installed and maintained by
Tenant, at Tenant's expense, on vibration eliminators or other devices
sufficient to reduce such noise and vibration to a level satisfactory to
Landlord. It is understood and agreed that as of the date of this Lease "NORMAL
ELECTRICAL USAGE" includes the use, for normal general office purposes, of
copying machines, personal or desk-top computers, standard small office servers,
printers, telephone systems,


                                       37
<PAGE>   40

televisions, VCRs and other standard office equipment used in the normal course
of office operation of first class office tenants in the North
Bethesda/Rockville Maryland area and which can be operated without exceeding the
Building's electrical capacity provided in accordance with the specifications
attached as Schedule I to Exhibit B hereto.

     11.2 (a) Subject to the provisions of this Article XI, Landlord hereby
grants to Tenant the right to use a portion of the roof of the Building in which
the Premises are located for the purpose of installing, operating, maintaining
in good condition and repair, repairing and replacing one (1) supplemental
cooling unit pursuant to the plans and specifications to be reviewed and
approved by Landlord in connection with the performance of the Tenant
Improvements in and to the Premises as described in Exhibit B hereof (the
"Rooftop Cooling Unit"). The Rooftop Cooling Unit shall be located and installed
on the roof of the Building in which the Premises are located in a location to
be approved by Landlord. The area on the roof of the Building in which the
Premises are located and on which the Rooftop Cooling Unit is to be placed is
referred to as the "Rooftop Equipment Space". Tenant's use of the Rooftop
Equipment Space shall be nonexclusive and Landlord shall at all times have
access to the Rooftop Equipment Space. Landlord retains the right to grant
licenses and other use and occupancy right to other tenants in the Complex and
to other third parties in Landlord's sole discretion. The Rooftop Cooling Unit
and the elements thereof may be replaced, as necessary, by Tenant in accordance
with the provisions of this Lease, provided such replacement is of equal or
better quality and workmanship and any damage caused by such replacement is
repaired promptly by Tenant at its expense.

         (b) Tenant, at its expense, shall remove the Rooftop Cooling Unit on or
before the expiration or earlier termination of the Lease Term, including,
without limitation, all cabling and hardware, and shall surrender the Rooftop
Equipment Space in the same condition as existed prior to Tenant's installation
of the Rooftop Cooling Unit, reasonable wear and tear and casualty damage which
is not the fault of Tenant excepted. Tenant shall be liable for and shall
promptly reimburse Landlord as additional rent for the cost of repairing all
damage to the Rooftop Equipment Space and/or the Building cause by such removal,
including filling and sealing any holes or cavities left by the removal of
cabling or hardware.

         (c) Tenant, at its sole cost and expense and at its sole risk, shall
cause the Rooftop Cooling Unit to be installed in a good and workmanlike manner,
and in compliance with all zoning, building, electric, communications and safety
laws, codes, ordinances, standards, regulations and requirements of the Federal
government, the State of Maryland, Montgomery County, the City of Rockville and
any other local jurisdiction in which the Complex is located. Tenant shall not
commence installation of such Rooftop Cooling Unit without the prior written
consent of Landlord in accordance with this Article XI. In no event shall
Tenant's installation of the Rooftop Cooling Unit damage the Building or the
existing installations on the Building or interfere with the maintenance of the
Building or any system serving the Building. Landlord, at its option, but at
Tenant's expense, may retain mechanical, electrical or structural engineers or
other consultants (i) to review Tenant's plans and specifications for the
Rooftop Cooling Unit and (ii) to supervise the installation, replacement,
repairs and removal of the Rooftop Cooling Unit. In the event Landlord retains
any such consultants during the Lease Term, Tenant shall pay to Landlord, as
additional rent hereunder, within thirty (30) days after receipt of an itemized


                                       38
<PAGE>   41

invoice the actual cost incurred by Landlord to retain such consultant(s).
Landlord's review and approval of the plans and specifications for the Rooftop
Cooling Unit and Landlord's inspection of the installation or operation thereof
shall not be construed in any way as approval by Landlord of the adequacy or
safety of the Rooftop Cooling Unit or of its installation or operation or as a
waiver of any of Landlord's rights hereunder, and Tenant shall be solely
responsible for the adequacy and safety of the installation and operation of the
Rooftop Cooling Unit and solely liable for any damages or injury arising out of
such installation and operation. Tenant shall pay to Landlord, as additional
rent hereunder, within thirty (30) days after receipt of an itemized invoice the
actual cost of repairing any damage to the Building caused by any such
installation. Landlord shall not be liable to Tenant for any cessation or
shortages of electrical power furnished to the Building except as otherwise
provided in Section 15.3 of this Lease. Tenant shall be liable to Landlord for
any actual damages suffered by Landlord from interruptions, stoppages or
shortages of electrical power or other services to the Building connected with
or arising out of the Rooftop Cooling Unit or Tenant's installation,
maintenance, operation, repair or removal thereof. Tenant's liability for such
actual damages shall be reduced by the amount of any insurance proceeds received
by Landlord on account of any such interruptions, stoppages or shortages of
electrical power or other services to the Building connected with or arising out
of the Rooftop Cooling Unit or Tenant's installation, maintenance, operation,
repair or removal thereof.

         (d) Tenant shall operate and maintain the Rooftop Cooling Unit in
strict compliance with the provisions of this Lease and applicable laws,
statutes, codes, rule, regulations, standards and requirements of all federal,
state and local governmental boards, authorities and agencies. Tenant, prior to
installing the Rooftop Cooling Unit shall have and shall deliver to Landlord
copies of all required permits, licenses and consents to install, operate,
maintain and repair the Rooftop Cooling Unit. Tenant covenants that the
installation and operation of the Rooftop Cooling Unit shall not interfere with
any existing rooftop equipment operated on or from the Building. In the event
that the operation of the Rooftop Cooling Unit violates any of the terms or
conditions of this Lease, Tenant agrees to suspend operation of the component of
the Rooftop Cooling Unit within twenty-four (24) hours after written notice from
Landlord or any governmental board, authority or agency of such violation and
Tenant shall not resume operation of the Rooftop Cooling Unit until its
operation is in strict compliance with all of the requirements of this Lease. In
the event Tenant refuses to suspend operation of the Rooftop Cooling Unit or in
the event of an emergency, Landlord shall have the right to suspend the supply
of electrical power to the Rooftop Cooling Unit and Landlord shall have no
liability to Tenant for such suspension.

         (e) Landlord makes no warranties or representations concerning the
suitability of the Rooftop Equipment Space for the installation, operation,
maintenance and repair of the Rooftop Cooling Unit, Tenant having satisfied
itself concerning such matters.

         (f) Tenant, at its sole cost and expense shall secure all necessary
permits and approvals from all applicable governmental authorities and agencies
with respect to the size, placement and installation of the Rooftop Cooling
Unit. In the event Tenant is unable to obtain the necessary approvals and
permits from any applicable federal, state, county or other local governing
authorities for the Rooftop Cooling Unit, Tenant shall have no remedy, claim,
cause


                                       39
<PAGE>   42

of action or recourse against Landlord, nor shall such failure or inability to
obtain any necessary permits or approvals provide Tenant the opportunity to
terminate this Lease.

         (g) Tenant's rights under this Section 11.2 are personal to OTG
Software, Inc. and may be exercised only by OTG Software, Inc. and any assignee
of OTG Software, Inc. permitted or approved by Landlord in accordance with the
provisions of Article VIII hereof.

                                   ARTICLE XII
                             INSPECTION BY LANDLORD

     12.1 Tenant will permit Landlord, its agents or representatives, to enter
the Premises, without charge therefor to Landlord and without diminution of the
rent payable by Tenant, to examine, inspect and protect the Premises and the
Building, to make such alterations or repairs as in the sole judgment of
Landlord may be deemed necessary, and to exhibit the same to prospective tenants
at any time during the last twelve (12) months of the Lease Term. In connection
with any such entry, Landlord and its agents shall be accompanied by a
representative of Tenant (except in cases of emergency or in cases where Tenant
fails to identify and make available such representative on the date of such
entry) and Landlord shall use reasonable efforts (i) to minimize the disruption
to Tenant's use of the Premises and (ii) to provide twenty-four (24) hours prior
notice to Tenant (except that no such notice shall be required in cases of
emergency). Except in cases of emergency, any entry by Landlord into the
Premises shall be subject to Tenant's reasonable security regulations, if any,
provided that Tenant has notified Landlord, in writing, of such regulations.

                                  ARTICLE XIII
                                    INSURANCE

     13.1 Tenant shall not conduct or permit to be conducted any activity, or
place any equipment in or about the Premises or the Building which will in any
way increase the rate of fire insurance or other insurance on the Building. If
any increase in the rate of fire insurance or other insurance is stated by any
insurance company or by the applicable Insurance Rating Bureau to be due to any
activity or equipment of Tenant in or about the Premises or the Building, such
statement shall be conclusive evidence that the increase in such rate is due to
such activity or equipment and, as a result thereof, Tenant shall be liable for
the amount of such increase. Tenant shall reimburse Landlord for such amount
upon written demand from Landlord and such sum shall be considered additional
rent payable hereunder.

     13.2 Throughout the Lease Term, Landlord shall insure the Building against
loss due to fire and other casualties included in standard extended coverage
insurance policies in an amount equal to at least 90% of the replacement cost
thereof, exclusive of architectural and engineering fees, excavations, footings
and foundations. Such insurance shall also cover the initial tenant improvements
installed in the Premises by Landlord in accordance with Exhibit B hereof in an
amount up to but not exceeding the Tenant Improvement Allowance, but shall not
cover (a) any amount to restore the Premises in excess of the Tenant Improvement
Allowance or (b) Tenant's furniture, fixtures, equipment or other personal
property of Tenant on the Premises. Throughout the Lease Term, Landlord shall
maintain commercial general liability insurance


                                       40
<PAGE>   43

covering the common areas of the Building (including without limitation
contractual liability coverage and broad form property damage) in amounts at
lease as high as the greater of (i) that required of Tenant under this Lease and
(ii) that required by Landlord's lender. At Tenant's written request Landlord
shall provide a copy of its insurance certificate showing general liability
insurance coverage.

     13.3 (a) Throughout the Lease Term, Tenant shall obtain and maintain (1)
commercial general liability insurance (written on an occurrence basis)
including contractual liability coverage insuring the obligations assumed by
Tenant under this Lease, premises and operations coverage, broad form property
damage coverage and independent contractors coverage, and containing an
endorsement for personal injury, (2) business interruption insurance, (3)
all-risk property insurance, (4) comprehensive automobile liability insurance
(covering any automobiles owned or operated by Tenant, if any), (5) worker's
compensation insurance, and (6) employer's liability insurance. Such commercial
general liability insurance shall be in minimum amounts typically carried by
prudent tenants engaged in similar operations, but in no event shall be in an
amount less than Two Million Dollars ($2,000,000) combined single limit per
occurrence with a Four Million Dollar ($4,000,000) annual aggregate. Such
business interruption insurance shall be in minimum amounts typically carried by
prudent tenants engaged in similar operations, but in no event shall be in an
amount less than the Base Rent then in effect during any Lease Year. Such
property insurance shall be in an amount not less than that required to replace
all of the original tenant improvements installed in the Premises pursuant to
Exhibit B, all Alterations and all other contents of the Premises (including,
without limitation, Tenant's trade fixtures, decorations, furnishings, equipment
and personal property). Such automobile liability insurance shall be in an
amount not less than One Million Dollars ($1,000,000) for each accident. Such
worker's compensation insurance shall carry minimum limits as defined by the law
of the jurisdiction in which the Building is located (as the same may be amended
from time to time). Such employer's liability insurance shall be in an amount
not less than One Million Dollars ($1,000,000) for each accident, One Million
Dollars ($1,000,000) disease-policy limit, and One Million Dollars ($1,000,000)
disease-each employee.

          (b) All such insurance shall: (1) be issued by a company that is
licensed to do business in the jurisdiction in which the Building is located,
that has been approved in advance by Landlord and that has a rating equal to or
exceeding A:IX from Best's Insurance Guide; (2) name Landlord, the managing
agent of the Building and the holder of any mortgage (as defined in Section
21.1) and any other person or entity reasonably designated by Landlord from time
to time as additional insureds and/or loss payees (as applicable); (3) contain
an endorsement that such policy shall remain in full force and effect
notwithstanding that the insured may have waived its right of action against any
party prior to the occurrence of a loss; (4) provide that the insurer thereunder
waives all right of recovery by way of subrogation against Landlord, its
partners, agents, employees, representatives and mortgage holders and all
trustees and beneficiaries with respect thereto, in connection with any loss or
damage covered by such policy; (5) be reasonably acceptable in form and content
to Landlord; (6) be primary and noncontributory; and (7) contain an endorsement
prohibiting cancellation, failure to renew, reduction of amount of insurance or
change in coverage without the insurer first giving Landlord thirty (30) days'
prior written notice (by certified or registered mail, return receipt requested)
of such proposed action. Subject to the provisions of Section 13.5 below, no
such policy shall


                                       41
<PAGE>   44
contain any deductible provision except as otherwise approved in writing by
Landlord, which approval shall not be unreasonably withheld. Landlord reserves
the right from time to time to require Tenant to obtain higher minimum amounts
of insurance, provided such higher minimum amounts are not inconsistent with the
requirements of owners of comparable buildings with respect to tenants of
comparable size in the City of Rockville, Montgomery County, Maryland area.
Tenant shall deliver a certificate of all such insurance and receipts evidencing
payment therefor (and, upon request, copies of all required insurance policies,
including endorsements and declarations) to Landlord on or before the Lease
Commencement Date and at least annually thereafter.

          (c) Tenant shall have the right to maintain the insurance coverages
set forth in this Article under a blanket insurance policy covering other
premises owned or leased by Tenant.

     13.4 Tenant hereby waives and releases Landlord and the holder of any
mortgage from any and all liabilities, claims and losses for which Landlord is
or may be held liable to the extent Tenant either is required to maintain
insurance pursuant to this Article XIII or receives insurance proceeds on
account thereof. Landlord hereby waives and releases Tenant from any and all
liabilities, claims and losses for which Tenant is or may be held liable to the
extent Landlord either is required to maintain insurance pursuant to this
Article XIII or receives insurance proceeds on account thereof. Both parties
shall secure waiver of subrogation endorsements from their respective insurance
carriers as to the other party. Landlord and Tenant agree that such waivers of
subrogation shall not apply to worker's compensation insurance.

     13.5 Notwithstanding anything to the contrary in this Article XIII, Tenant
may satisfy the insurance requirements set forth in Section 13.3 above through a
corporate-wide self- insurance program; provided, however, that Tenant's use of
such corporate-wide self-insurance program to satisfy the requirements of
Section 13.3 shall be subject to Landlord's prior review of and consent to such
corporate-wide self-insurance program. If Tenant elects to self-insure, it shall
provide Landlord with all of the same coverage and protection with which
Landlord would otherwise be provided by Tenant under this Article. During any
period that Tenant decides to self-insure, it shall provide Landlord with a copy
of each of its most recently published financial statements. Landlord hereby
approves Tenant's self-insurance of its personal property.

                                   ARTICLE XIV
                             SERVICES AND UTILITIES

     14.1 Landlord shall furnish to the Premises year-round ventilation and air
conditioning and heat during normal hours of operation of the Building, as
hereinafter provided, during the seasons when such utilities are required in
accordance with the specifications attached hereto as Schedule I to Exhibit B.
Landlord shall also provide reasonably adequate electricity (in accordance with
the specifications set forth on Schedule I to Exhibit B attached hereto), water,
exterior window-cleaning service, and char and janitorial service (after 6:00
p.m.) on Monday through Friday only, excluding legal holidays, in accordance
with the janitorial specifications outlined in Exhibit E attached hereto.
Landlord will also provide elevator service; provided, however, that Landlord
shall have the right to remove elevators from service as may be required for
moving freight, or for servicing or maintaining the elevators or the Building.
At least one


                                       42
<PAGE>   45

elevator cab shall be available for use by Tenant at all times. Tenant, at
Tenant's sole cost and expense, and subject to Landlord's review and approval
which shall not be unreasonably withheld, conditioned or delayed, may install a
"lock out" protection system to the elevators in the Building. The normal hours
of operation of the Building (including the provision of HVAC service) will be
7:30 a.m. to 7:00 p.m. on Monday through Friday (except legal holidays) and 8:00
a.m. to 2:00 p.m. on Saturday (except legal holidays). There will be no normal
hours of HVAC operation of the Building on Sundays or legal holidays, and
Landlord shall not be obligated to maintain or operate the Building at such
times unless special arrangements are made by Tenant. The services and utilities
required to be furnished by Landlord, other than electricity and water, will be
provided only during the normal hours of operation of the Building, except as
otherwise specified herein. It is agreed that if Tenant requires air
conditioning or heat beyond the normal hours of operation set forth herein,
Landlord will furnish such air conditioning or heat, provided Tenant gives
Landlord's agent sufficient advance notice of such requirement and Tenant agrees
to pay for the cost of such extra service in accordance with Landlord's then
current schedule of costs and assessments for such extra service. In the event
Tenant requires such extra service, Tenant must notify Landlord's tenant
coordinator/property manager, no later than (a) 2 p.m. the day such extra
service is required if such extra service is required on a weekday which is not
a federal holiday, (b) 2 p.m. on Friday in the event such extra service is
required the next Saturday, Sunday or federal holiday which is on a Monday, or
(c) 2 p.m. on the day preceding any federal holiday which is not on a Monday, as
applicable. Landlord agrees to provide an access-control system in the Building
comparable to the system in first-class office buildings in the City of
Rockville, Montgomery County, Maryland area, which shall permit Tenant to have
access to the Premises on a 24-hour, seven-days-a-week basis (except in the
event of emergency). Landlord, at its cost, shall provide Tenant an initial set
of security access cards to the Building in an amount up to one (1) card for
each of Tenant's and NOS's employees who will be working in the Building on the
Lease Commencement Date; provided, however, that any additional or replacement
cards shall be provided by Landlord and Tenant shall reimburse Landlord, as
additional rent, for Landlord's cost thereof.

     14.2 It is understood and agreed that Landlord shall not have any liability
to Tenant whatsoever as a result of Landlord's failure or inability to furnish
any of the utilities or services required to be furnished by Landlord hereunder,
whether resulting from breakdown, removal from service for maintenance or
repairs, strikes, scarcity of labor or materials, acts of God, governmental
requirements, or any other cause whatsoever. It is further agreed that any such
failure or inability to furnish the utilities or services required hereunder
shall not be considered an eviction, actual or constructive, of the Tenant from
the Premises, and shall not entitle Tenant to terminate this Lease or to an
abatement of any rent payable hereunder.

     14.3 (a) Notwithstanding the provisions of Section 14.2 to the contrary, if
(i) the services described in Section 14.1 hereof are interrupted for a period
of more than five (5) consecutive business days and (ii) such interruption
renders all or a substantial portion of the Premises untenantable by Tenant,
then, as Tenant's sole and exclusive remedy therefor, Tenant shall be entitled
to a pro rata abatement of base rent and additional rent attributable to
Operating Expenses beginning on the sixth (6th) consecutive business day that
the Premises are unusable and continuing until the use of the Premises is
restored to Tenant.


                                       43
<PAGE>   46

          (b) Landlord will use its commercially reasonable to cause the
restoration of any interrupted utility services; further, should any equipment
or machinery in the Building break down so as to render the Premises unusable by
Tenant, Landlord shall promptly repair or replace it (subject to delays which
result from strikes, unavailability of parts or other materials, or other
matters beyond Landlord's reasonable control).

     14.4 The parties hereto agree to comply with all mandatory energy
conservation controls and requirements applicable to office buildings that are
imposed or instituted by the Federal, state or local governments, including
without limitation, controls on the permitted range of temperature settings in
office buildings, and requirements necessitating curtailment of the volume of
energy consumption or the hours of operation of the Building. Any terms or
conditions of this Lease that conflict or interfere with compliance with such
controls or requirements shall be suspended for the duration of such controls or
requirements. It is further agreed that compliance with such controls or
requirements shall not be considered an eviction, actual or constructive, of the
Tenant from the Premises and shall not entitle Tenant to terminate this Lease or
to an abatement of any rent payable hereunder.

     14.5 Tenant shall reimburse Landlord for any excess water usage in the
Premises. "EXCESS WATER USAGE" shall mean the excess of Tenant's water usage
during any billing period for water services over the estimated average water
usage during the same period for all office tenants of the Building (excluding
Tenant), as computed by Landlord. If Tenant connects into Landlord's
supplemental cooling system currently located on the roof of the Building, then
Tenant shall reimburse Landlord for all costs incurred by Landlord therefor, as
reasonably determined by Landlord. Landlord may install checkmeters to
electrical circuits serving Tenant's equipment to verify that Tenant is not
consuming excessive electricity. If such checkmeters indicate that Tenant's
electricity consumption is excessive, then Landlord may install at Tenant's
expense submeters to ascertain Tenant's actual electricity consumption, and
Tenant shall thereafter pay for such consumption at the then-current price per
kilowatt hour charged Landlord by the utility. Tenant's electricity consumption
shall be deemed excessive if the electricity consumption in the Premises per
square foot of rentable area (including, without limitation, electricity
consumed in connection with outlets and lighting use) during any billing period
exceeds the average electricity consumption per square foot of rentable area
during the same period for typical, similarly situated tenants in the Building,
as reasonably calculated by Landlord. Landlord agrees that normal use of the
improvements to be constructed in the Premises in accordance with Exhibit B
which utilize water, shall not be considered Excess water usage.

     14.6 Tenant, in connection with the work to be performed pursuant to the
Work Agreement attached hereto as Exhibit B, may elect, at its expense which may
be paid out of the Improvements Allowance, to cause a separate electrical meter
or meters, as required, to be installed in the Premises for the purpose of
measuring electrical power furnished exclusively to the Premises. In the event
Tenant elects to have separate electrical meters or submeters installed, (a)
Tenant agrees to pay all applicable utility bills when due directly to the
utility company or upon presentation thereof by Landlord, (b) Tenant agrees to
indemnify and hold Landlord harmless from and against any claims made by any
electric utility companies which arise from Tenant's use of such utilities or
from Tenant's failure to pay any bill rendered for electric utilities


                                       44
<PAGE>   47

furnished to the Premises, (c) the electricity component of Operating Expenses
with respect to the Premises shall be deleted from the calculation of Operating
Expenses to be paid by Tenant in accordance with the provisions of Article IV
hereof and (d) the base rent shall be reduced appropriately.

     14.7 Subject to applicable regulatory prohibitions promulgated after the
date of this Lease and the availability of insurance at commercially reasonable
rates, the Building shall contain a shower facility (subject to reasonable rules
and regulations applicable to all Building tenants) on the lower level of the
Building. The shower facility shall be available to Tenant's employees on a
non-exclusive first-come, first-served basis. Such use shall be free of charge
during the initial Lease Term. Landlord shall not be liable to Tenant or any of
its employees or others for injuries received by such parties while using the
shower facility, and Tenant agrees to indemnify and save harmless Landlord from
any such liability except to the extent resulting from the negligence or willful
misconduct of Landlord or its employees. Landlord may specifically condition the
use of the shower facility by any person upon such person's execution of a
written waiver and release holding Landlord harmless from any and all liability,
damage, expense, cause of action, suit, claim, judgment and cost of defense
arising from injury to such employee or guest occurring in the shower facility
or resulting from the use thereof.

                                   ARTICLE XV
                              LIABILITY OF LANDLORD

     15.1 Except as otherwise expressly provided in this Lease, Landlord shall
not be liable to Tenant, its employees, agents, business invitees, licensees,
customers, clients, family members or guests for any damage, injury, loss,
compensation or claim, including but not limited to claims for the interruption
of or loss to Tenant's business, based on, arising out of or resulting from any
cause whatsoever, including but not limited to the following: repairs to any
portion of the Premises or the Building; interruption in the use of the
Premises; any accident or damage resulting from the use or operation (by
Landlord, Tenant or any other person or persons) of elevators, or of the
heating, cooling, electrical or plumbing equipment or apparatus; the termination
of this Lease by reason of the destruction of the Premises or the Building; any
fire, robbery, theft, mysterious disappearance or any other casualty; the
actions of any other tenants of the Building or of any other person or persons;
and any leakage in any part or portion of the Premises or the Building, or from
water, rain or snow that may leak into, or flow from, any part of the Premises
or the Building, or from drains, pipes or plumbing fixtures in the Building. Any
goods, property or personal effects stored or placed by Tenant or its employees
in or about the Premises or the Building shall be at the sole risk of Tenant,
and Landlord shall not in any manner be held responsible therefor. It is
understood that the employees of Landlord are prohibited from receiving any
packages or other articles delivered to the Building for Tenant, and if any such
employee receives any such package or articles, such employee shall be acting as
the agent of Tenant for such purposes and not as the agent of Landlord.
Notwithstanding the foregoing provisions of this Section 15.1 to the contrary,
Landlord shall not be released from liability to Tenant for damage or injury
caused by the negligence or willful misconduct of Landlord or its employees or
caused by the gross negligence or willful misconduct of Landlord's agents or
contractors; provided, however, in no event shall Landlord have any liability to
Tenant for any claims based on the interruption of or loss to Tenant's business
(except for the rent abatement


                                       45
<PAGE>   48

provided pursuant to Section 14.3) or for any indirect losses or consequential
damages whatsoever.

     15.2 Tenant hereby agrees to indemnify and hold Landlord harmless from and
against all costs, damages, claims, liabilities and expenses (including
reasonable attorneys' fees and any costs of litigation) suffered by or claimed
against Landlord, directly or indirectly, based on, arising out of or resulting
from (i) Tenant's use or occupancy of the Premises or the business conducted by
Tenant therein, (ii) any accident, injury or damage whatsoever caused to any
person, or to the property of any person, occurring in the Premises during the
Lease Term, except to the extent resulting from the negligence or willful
misconduct of Landlord or its employees or the gross negligence or willful
misconduct of Landlord's agents or contractors, (iii) any act or omission to act
by Tenant or its employees, contractors, agents, licensees, or invitees, (iv)
any breach or default by Tenant in the performance or observance of its
covenants or obligations under this Lease, (v) the towing of any car or other
vehicle as provided in Section 24.3 hereof or (vi) Tenant's failure to comply
with any requirements imposed in connection with the Tax Reduction described in
Section 4.1(c) above. Tenant's obligation to indemnify Landlord pursuant to this
Section shall be applicable and shall be enforceable only to the extent that
Landlord has suffered an actual and demonstrable loss directly and solely caused
by the breach or default by Tenant in the performance or observance of its
covenants or obligations under this Lease, including without limitation, those
set forth in the preceding sentence; and provided, however, in no event shall
Tenant have any liability to Landlord under this Section 15.2 for any indirect
losses or consequential damages whatsoever or for claims which Landlord is
insured or required under this Lease to be insured.

     15.3 Landlord hereby agrees to indemnify and hold Tenant harmless from and
against all costs, damages, claims, liabilities and expenses (including
reasonable attorney's fees and costs of litigation) suffered by or claimed
against Tenant, directly or indirectly, based on, arising out of or resulting
from (i) any accident, injury or damage whatsoever caused to any person, or the
property of any person, on or about the common or public areas of the Building
during the Lease Term or (ii) any breach or default by Landlord in the
performance or observance of its covenants or obligations under this Lease;
except, to the extent such accident, injury, damage, failure, breach or default
is a result of or in any way caused by Tenant's or any of its agents,
contractors, employees' or subtenant's negligence or willful misconduct and
except, further, that Landlord's obligation to indemnify Tenant pursuant to
Sections 15.3 (ii) and (iii) above shall be applicable and shall be enforceable
only to the extent that Tenant has suffered an actual and demonstrable loss
directly and solely caused by the breach or default by Landlord in the
performance or observance of its covenants or obligations under this Lease; and
provided, however, that in no event shall Landlord have any liability to Tenant
for claims based on the interruption of or loss to Tenant's business (except for
the rent abatement provided pursuant to Section 14.3) or for any indirect losses
or consequential damages whatsoever or for claims for which Tenant is insured or
required under this Lease to be insured. Notwithstanding anything to the
contrary in this Section 15.3 or elsewhere in this Lease, this Section 15.3
shall not apply to the holder of any mortgage or deed of trust secured by the
Building unless and until such holder owns or holds title to the Building by
foreclosure or deed-in-lieu of foreclosure, and in such case, only as to matters
arising during the period of such ownership.


                                       46
<PAGE>   49

     15.4 In the event that at any time Landlord shall sell or transfer title to
the Building, provided the purchaser or transferee assumes, in writing, the
obligations of Landlord hereunder arising from and after the date of the
transfer, the Landlord named herein shall not be liable to Tenant for any
obligations or liabilities based on or arising out of events or conditions
occurring on or after the date of such sale or transfer. Furthermore, Tenant
agrees to attorn to any such purchaser or transferee upon all the terms and
conditions of this Lease.

     15.5 In the event that at any time during the Lease Term Tenant shall have
a claim against Landlord, Tenant shall not have the right to deduct the amount
allegedly owed to Tenant from any rent or other sums payable to Landlord
hereunder, it being understood that Tenant's sole remedy for recovering upon
such claim shall be to institute an independent action against Landlord.

     15.6 Tenant agrees that in the event Tenant is awarded a money judgment
against Landlord, Tenant's sole recourse for satisfaction of such judgment shall
be limited to execution against the estate and interest of Landlord in the
Building. In no event shall any other assets of Landlord, any partner of
Landlord, the holder of any mortgage (or anyone claiming by through or under
such holder) or any other person or entity be available to satisfy, or be
subject to, such judgment, nor shall any partner of Landlord or any such other
person or entity be held to have any personal liability for satisfaction of any
claims or judgments that Tenant may have against Landlord or any partner of
Landlord in such partner's capacity as a partner of Landlord. Notwithstanding
the provisions of this section 15.6 to the contrary, for so long as Landlord is
Boston Properties Limited Partnership, in the event (i) Tenant shall recover a
final and unreviewable judgment (that is, an unappealable judgment or a judgment
for which the applicable appeal period shall have expired) against Landlord
subsequent to the date on which Landlord shall have divested or transferred its
estate and interest in the Building (whether voluntary or by virtue of the
exercise by the holder of any of its right of foreclosure thereunder), and (ii)
Tenant shall therefore have no effective recourse against Landlord's transferred
estate or interest in the Building, then, in such event, Tenant shall have the
right to pursue the enforcement of such judgment against the personal assets of
Landlord.

                                   ARTICLE XVI
                              RULES AND REGULATIONS

     16.1 Tenant and its agents, employees, invitees, licensees, customers,
clients, family members, guests and permitted subtenants shall at all times
abide by and observe the rules and regulations attached hereto as Exhibit C. In
addition, Tenant and its agents, employees, invitees, licensees, customers,
clients, family members, guests and permitted subtenants shall abide by and
observe all other rules or regulations that Landlord may promulgate from time to
time for the operation and maintenance of the Building, provided that reasonable
advance notice thereof is given to Tenant and such rules and regulations are
non-discriminatory and not inconsistent with the provisions of this Lease.
Nothing contained in this Lease shall be construed as imposing upon Landlord any
duty or obligation to enforce such rules and regulations, or the terms,
conditions or covenants contained in any other lease, as against any other
tenant, and Landlord shall not be liable to Tenant for the violation of such
rules or regulations by any other tenant or its employees, agents, business
invitees, licensees, customers, clients, family members or guests.


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<PAGE>   50

Landlord shall use commercially reasonable efforts to enforce all such rules and
regulations, including any exceptions thereto, uniformly and in a manner which
does not unreasonably discriminate against Tenant, or increase Tenant's monetary
obligations under this Lease, although it is understood that Landlord may grant
exceptions to such rules and regulations in circumstances in which it reasonably
determines such exceptions are warranted. If there is any inconsistency between
this Lease and the Rules and Regulations set forth in Exhibit C, this Lease
shall govern.

                                  ARTICLE XVII
                              DAMAGE OR DESTRUCTION

     17.1 If, during the Lease Term, the Premises or the Building are totally or
partially damaged or destroyed from any cause, thereby rendering the Premises
totally or partially inaccessible or unusable, Landlord shall diligently (taking
into account the time necessary to effectuate a satisfactory settlement with any
insurance company involved) restore and repair the Premises and the Building to
substantially the same condition they were in prior to such damage; provided,
however, if in the sole but not unreasonable judgment of Landlord the repairs
and restoration cannot be completed within one hundred eighty (180) days after
the occurrence of such damage, including the time needed for removal of debris,
preparation of plans and issuance of all required governmental permits, Landlord
shall have the right, at its sole option, to terminate this Lease by giving
written notice of termination to Tenant within forty-five (45) days after the
occurrence of such damage. Landlord shall use reasonable efforts not to
discriminate against Tenant in determining whether to exercise its right to
terminate this Lease in accordance with the provisions of this Section 17.1.

     17.2 (a) If in the reasonable professional judgment of Landlord's
architect, as set forth in a written report, a copy of which shall be provided
to Tenant, that the repairs and restoration cannot be substantially completed
within one hundred eighty (180) days after the date of such damage or
destruction, Landlord shall promptly notify Tenant of such determination and the
date by which Landlord reasonably estimates it could substantially complete such
repairs and restoration (the "Estimated Restoration Date") and shall deliver to
Tenant a copy of the architect's written report. For a period of thirty (30)
days after receipt of such determination, Tenant shall have the right to
terminate this Lease by providing written notice to Landlord. If Tenant does not
elect to terminate this Lease within such thirty (30) day period, and provided
that Landlord has not elected to terminate this Lease, Landlord shall proceed to
repair and restore the Premises (including the means of access thereto) and the
Building. Notwithstanding the foregoing, Tenant shall not have the right to
terminate this Lease if the gross negligence or willful misconduct of Tenant, or
any of its employees, agents, contractors, licensees, subtenants or Invitees,
shall have caused the damage or destruction.

          (b) If this Lease is not terminated pursuant to the provisions of
either Section 17.1 or Section 17.2 hereof, but the repairs and restoration of
the Premises undertaken by Landlord are not substantially completed on or before
the sixtieth (60th) day after the Estimated Restoration Date (the "Restoration
Deadline"), then Tenant shall have the right to terminate this Lease by
delivering written notice of the exercise of such right to Landlord within five
(5) days after such Restoration Deadline. Notwithstanding the foregoing, the
Restoration Deadline shall


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<PAGE>   51

be extended on a day-for-day basis to the extent any of the following factors
delay the repair and restoration of the Premises: (i) if the delay in completion
is a result of the willful act or negligence of Tenant, its agents, employees,
contractors, or consultants; or (ii) if (x) the delay in completion is the
result of reasons or causes not the fault of Landlord and which Landlord could
not have reasonably foreseen and provided for including, without limitation,
strikes, acts of God, unavailability of materials and other causes beyond the
reasonable control of Landlord, (y) Landlord has given Tenant notice of such
delay and (z) the necessary repairs and restoration are substantially completed
within one hundred twenty (120) days after the Estimated Restoration Date (the
"Extended Restoration Deadline"). In the event the necessary repairs and
restoration are not substantially completed on or before the Extended
Restoration Date and the delay in completion is not the result of the willful
act or negligence of Tenant, its agents, employees, contractors, or consultants,
then Tenant shall have the right to terminate this Lease by delivering written
notice of the exercise of such right to Landlord within five (5) days after the
Extended Restoration Deadline.

     17.3 If this Lease is terminated pursuant to Section 17.1 or Section 17.2
above, all rent payable hereunder shall be apportioned and paid to the date of
the occurrence of such damage, and Tenant shall have no further rights or
remedies as against Landlord pursuant to this Lease, or otherwise. If this Lease
is not terminated as a result of such damage, and provided that such damage was
not caused by the gross negligence or willful misconduct of Tenant, or any of
its employees, agents, contractors, licensees, subtenants or Invitees until the
repair and restoration of the Premises is completed Tenant shall be required to
pay annual base rent and additional rent only for that part of the Premises that
Tenant is able to use while repairs are being made, based on the ratio that the
amount of usable rentable area bears to the total rentable area of the Premises;
however, if such damage or destruction was caused by the gross negligence or
willful misconduct of Tenant, of any of its employees, agents, contractors,
licensees, subtenants or Invitees then the aforesaid rent abatement shall apply
only to the extent Landlord receives rent loss insurance proceeds with respect
to the Premises. Landlord shall bear the costs and expenses of repairing and
restoring the Premises, except that if such damage or destruction was caused by
the gross negligence or willful misconduct of Tenant, of any of its employees,
agents, contractors, licensees, subtenants or Invitees upon written demand from
Landlord, Tenant shall pay to Landlord the amount by which such costs and
expenses exceed the insurance proceeds, if any, received by Landlord on account
of such damage or destruction (or would have been available to Landlord had
Landlord maintained standard extended coverage insurance policies in an amount
equal to 100% of the replacement cost of the Building). Provided, however, that
Landlord shall not be obligated to restore the Premises or the Building if (a)
the destruction was not caused by an insurable event or (b) the estimated cost
of such restoration, as determined by Landlord's architect, exceeds the amount
of insurance proceeds available to Landlord for such restoration by more than
ten percent (10%) of such amount or more (or which would have been available to
Landlord maintained standard extended coverage insurance policies in an amount
equal to 100% of the replacement cost of the Building), in which event, Landlord
shall promptly notify Tenant of such determination..

     17.4 If Landlord repairs and restores the Premises as provided in this
Article XVII, Landlord shall not be required to repair or restore any
decorations, alterations or improvements to the Premises previously made by or
at the expense of Tenant (other than such portion of the


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<PAGE>   52

Tenant Improvements installed in the Premises in accordance with Exhibit B
hereof, in an amount up to the greater of the amount of the Tenant Improvement
Allowance or the actual cost of constructing and installing those initial Tenant
Improvements in the Premises which will remain in the Premises after the
expiration or earlier termination of the Lease Term) nor any of the trade
fixtures, furnishings, equipment or personal property belonging to Tenant. It
shall be Tenant's sole responsibility to repair and restore all such items.

     17.5 Notwithstanding anything to the contrary contained herein, if the
Building is damaged or destroyed from any cause to such an extent that the costs
of repairing and restoring the Building would exceed fifty percent (50%) of the
replacement value of the Building, whether or not the Premises are damaged or
destroyed, Landlord shall have the right to terminate this Lease by written
notice to Tenant, provided the leases of all other similarly affected tenants in
the Building are terminated and Landlord in fact does not repair or restore the
damaged or destroyed portions of the Building within the six (6) month period
following the date of termination. This right of termination shall be in
addition to any other right of termination provided in this Lease.

                                  ARTICLE XVIII
                                  CONDEMNATION

     18.1 If the whole or a substantial part (as hereinafter defined) of the
Building or the Premises, or the use or occupancy of a substantial part of the
Premises, shall be taken or condemned by any governmental or quasi-governmental
authority for any public or quasi-public use or purpose (including a sale
thereof under threat of such a taking), then this Lease shall terminate on the
date title thereto vests in such governmental or quasi-governmental authority,
and all rent payable hereunder shall be apportioned as of such date. If less
than a substantial part of the Premises, or the use or occupancy thereof, is
taken or condemned by any governmental or quasi-governmental authority for any
public or quasi-public use or purpose (including a sale thereof under threat of
such a taking), this Lease shall continue in full force and effect, but the
annual base rent and additional rent thereafter payable hereunder shall be
equitably adjusted (on the basis of the ratio of the number of square feet of
rentable area taken to the total rentable area of the Premises prior to such
taking) as of the date title vests in the governmental or quasi-governmental
authority. For purposes of this Article XVIII, a substantial part of the
Building or the Premises shall be considered to have been taken if more than
one-third (1/3) of the Building or the Premises is rendered unusable as a result
of such taking or the number of parking spaces in the parking deck or surface
parking areas appurtenant to the Building is reduced by more than one-third
(1/3).

     18.2 All awards, damages and other compensation paid by the condemning
authority on account of such taking or condemnation (or sale under threat of
such taking) shall belong to Landlord, and subject to the provisions of this
Section 18.2 with respect to Tenant's right to make a claim against the
condemning authority, Tenant hereby assigns to Landlord all rights to such
awards, damages and compensation. Tenant agrees not to make any claim against
the Landlord or the condemning authority for any portion of such award or
compensation attributable to damage to the Premises, the value of the unexpired
term of this Lease, the loss of profits or goodwill, leasehold improvements or
severance damages. Nothing contained herein,


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<PAGE>   53

however, shall prevent Tenant from pursuing a separate claim against the
condemning authority for the value of furnishings, equipment and trade fixtures
installed in the Premises at Tenant's expense and for relocation expenses,
provided that such claim does not in any way diminish the award or compensation
payable to or recoverable by Landlord in connection with such taking or
condemnation. Landlord agrees that it shall not make a claim for the value of
Tenant's furnishings, equipment or trade fixtures installed in the Premises by
Tenant, at Tenant's expense.

     18.3 In the event there is a taking (a "Taking") of a substantial part of
the Premises as described in Section 18.1, and this Lease is not terminated or
if there is less than a substantial taking, Landlord shall proceed with due
diligence to make all necessary repairs to the Premises, the Building and/or the
parking deck, as defined in Section 24.1 below, or surface parking area in order
to render the same to substantially the same condition that they were in prior
to the Taking. Notwithstanding the provisions of Section 18.1 above to the
contrary, in the event that (a) Landlord does not provide Tenant with one (1)
copy of the proposed plans (the "Reconstruction Plans") for the reconstruction
or repair of the Premises within sixty (60) days of the effective date of the
Taking, (b) the restoration of the Premises cannot be completed within one
hundred eighty (180) days of the effective date of the Taking, (c) Tenant does
not retain the right to a proportionate number of parking permits in the parking
deck and/or the surface parking areas as Tenant had immediately prior to the
Taking or (d) Tenant does not have access to the Building and the Premises at
all times during the normal hours of operation of the Building as set forth in
Section 14.1 above during such period of repair and reconstruction, then Tenant
may terminate this Lease as of the effective date of the Taking by giving notice
of the exercise of the option to terminate this Lease to the other party not
more than thirty (30) days after the date on which Landlord delivers or should
have delivered the Reconstruction Plans to Tenant.

                                   ARTICLE XIX
                                DEFAULT BY TENANT

     19.1 The occurrence of any of the following shall constitute an Event of
Default by Tenant under the Lease:

          (a) If Tenant shall fail to pay any installment of annual base rent or
additional rent or any other sums required by this Lease when due and such
failure shall remain uncured for a period of ten (10) days after Tenant receives
written notice of such failure; provided, however, that Landlord shall not be
required to give Tenant more than two (2) such written notices in any twelve
(12) month period.

          (b) If Tenant shall violate or fail to perform any other term,
condition, covenant or agreement to be performed or observed by Tenant under
this Lease and such violation or failure shall continue uncured for a period of
thirty (30) days after Tenant receives written notice of such violation or
failure. If such violation or failure is not capable of being cured within such
thirty (30) day period, no Event of Default shall be deemed to have occurred
hereunder if Tenant commences curative action within such thirty (30) day period
and proceeds diligently and in good faith thereafter to cure such violation or
failure until completion.

          (c) [Intentionally Deleted]


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<PAGE>   54

          (d) If an Event of Bankruptcy, as defined in Section 20.1 of this
Lease, shall occur.

     19.2 If there shall be an Event of Default (even if prior to the Lease
Commencement Date), then the provisions of this Section shall apply. Landlord
shall have the right, at its sole option, to terminate this Lease. In addition,
with or without terminating this Lease, Landlord may reenter, terminate Tenant's
right of possession and take possession of the Premises. The provisions of this
Article shall operate as a notice to quit, and Tenant hereby waives any other
notice to quit or notice of Landlord's intention to reenter the Premises or
terminate this Lease. If necessary, Landlord may proceed to recover possession
of the Premises under applicable Laws, or by such other lawful proceedings,
including reentry and possession, as may be applicable. If Landlord elects to
terminate this Lease and/or elects to terminate Tenant's right of possession,
everything contained in this Lease on the part of Landlord to be done and
performed shall cease without prejudice, however, to Tenant's liability for all
base rent, additional rent and other sums specified herein. Whether or not this
Lease and/or Tenant's right of possession is terminated, Landlord shall have the
right, at its sole option, to terminate any renewal or expansion right contained
in this Lease and to grant or withhold any consent or approval pursuant to this
Lease in its sole and absolute discretion; provided, however that so long as no
more than three (3) monetary or non-monetary material events of default beyond
any applicable notice and cure shall have occurred, Tenant's rights that may
have been terminated pending such event of default shall be reinstated. Landlord
shall use commercially reasonable efforts to relet the Premises or any part
thereof, alone or together with other premises, for such term(s) (which may
extend beyond the date on which the Lease Term would have expired but for
Tenant's default) and on such terms and conditions (which may include any
concessions or allowances granted by Landlord) as Landlord, in its sole and
absolute discretion, may determine, but Landlord shall not be liable for, nor
shall Tenant's obligations hereunder be diminished by reason of, any failure by
Landlord to relet all or any portion of the Premises or to collect any rent due
upon such reletting. Whether or not this Lease and/or Tenant's right of
possession is terminated or any suit is instituted, Tenant shall be liable for
any base rent, additional rent, damages or other sum which may be due or
sustained prior to such default, and for all costs, fees and expenses
(including, but not limited to, reasonable attorneys' fees and costs, brokerage
fees, expenses incurred in enforcing any of Tenant's obligations under the Lease
or in placing the Premises in first-class rentable condition, advertising
expenses, and any concessions or allowances granted by Landlord) incurred by
Landlord in pursuit of its remedies hereunder and/or in recovering possession of
the Premises and renting the Premises to others from time to time plus other
actual damages suffered or incurred by Landlord on account of Tenant's default
(including, but not limited to late fees or other charges incurred by Landlord
under any mortgage). Notwithstanding anything to the contrary in this Section
19.2, Tenant expressly acknowledges that Landlord's agreement to use
commercially reasonable efforts to relet the Premises shall in no event limit,
restrict or prejudice Landlord's right to lease all other vacant space in the
Building or the Complex prior to reletting the Premises. Tenant also shall be
liable for additional damages which at Landlord's election shall be either one
or a combination of the following: (a) an amount equal to the Base Rent and
additional rent due or which would have become due from the date of Tenant's
default through the remainder of the Lease Term, less the amount of rental, if
any, which Landlord receives during such period from others to whom the Premises
may be rented (other than any additional


                                       52
<PAGE>   55

rent received by Landlord as a result of any failure of such other person to
perform any of its obligations to Landlord), which amount shall be computed and
payable in monthly installments, in advance, on the first day of each calendar
month following Tenant's default and continuing until the date on which the
Lease Term would have expired but for Tenant's default, it being understood that
separate suits may be brought from time to time to collect any such damages for
any month(s) (and any such separate suit shall not in any manner prejudice the
right of Landlord to collect any damages for any subsequent month(s)), or
Landlord may defer initiating any such suit until after the expiration of the
Lease Term (in which event such deferral shall not be construed as a waiver of
Landlord's rights as set forth herein and Landlord's cause of action shall be
deemed not to have accrued until the expiration of the Lease Term), and it being
further understood that if Landlord elects to bring suits from time to time
prior to reletting the Premises, Landlord shall be entitled to its full damages
through the date of the award of damages without regard to any Base Rent,
additional rent or other sums that are or may be projected to be received by
Landlord upon reletting of the Premises; or (b) an amount equal to the sum of
(i) all base rent, additional rent and other sums due or which would be due and
payable under this Lease as of the date of Tenant's default through the end of
the scheduled Lease Term, plus (ii) the all expenses (including reasonable
attorneys' fees) projected by Landlord to be incurred in connection with the
reletting of the Premises, other than brokerage commissions and the value of all
vacancy periods, minus (iii) any base rent, additional rent and other sums which
Tenant proves by a preponderance of the evidence would be received by Landlord
upon reletting of the Premises from the end of the vacancy period projected by
Landlord through the expiration of the scheduled Lease Term. Such amount shall
be discounted using a discount factor equal to the yield of the Treasury Note or
Bill, as appropriate, having a maturity period approximately commensurate to the
remainder of the Term, and such resulting amount shall be payable to Landlord in
a lump sum on demand, it being understood that upon payment of such liquidated
and agreed final damages, Tenant shall be released from further liability under
this Lease with respect to the period after the date of such payment, and that
Landlord may bring suit to collect any such damages at any time after an Event
of Default shall have occurred. In the event Landlord relets the Premises
together with other premises or for a term extending beyond the scheduled
expiration of the Lease Term, it is understood that Tenant will not be entitled
to apply any base rent, additional rent or other sums generated or projected to
be generated by either such other premises or in the period extending beyond the
scheduled expiration of the Lease Term (collectively, the "EXTRA RENT") against
Landlord's damages. Similarly in proving the amount that would be received by
Landlord upon a reletting of the Premises as set forth in clause (iii) above,
Tenant shall not take into account the Extra Rent. The provisions contained in
this Section shall be in addition to, and shall not prevent the enforcement of,
any claim Landlord may have against Tenant for anticipatory breach of this
Lease. Nothing herein shall be construed to affect or prejudice Landlord's right
to prove, and claim in full, unpaid rent accrued prior to termination of this
Lease. If Landlord is entitled, or Tenant is required, pursuant to any provision
hereof to take any action upon the termination of the Lease Term, then Landlord
shall be entitled, and Tenant shall be required, to take such action also upon
the termination of Tenant's right of possession.

     19.3 (a) Tenant hereby expressly waives, for itself and all persons
claiming by, through or under it, any right of redemption, reentry or
restoration of the operation of this Lease under any present or future Law,
including without limitation any such right which Tenant would


                                       53
<PAGE>   56

otherwise have in case Tenant shall be dispossessed for any cause, or in case
Landlord shall obtain possession of the Premises as herein provided.

          (b) All rights and remedies of Landlord set forth herein are in
addition to all other rights and remedies available to Landlord hereunder or at
law or in equity. All rights and remedies available to Landlord hereunder or at
law or in equity are expressly declared to be cumulative. The exercise by
Landlord of any such right or remedy shall not prevent the concurrent or
subsequent exercise of any other right or remedy. No delay in the enforcement or
exercise of any such right or remedy shall constitute a waiver of any default by
Tenant hereunder or of any of Landlord's rights or remedies in connection
therewith. Landlord shall not be deemed to have waived any default by Tenant
hereunder unless such waiver is set forth in a written instrument signed by
Landlord. If Landlord waives in writing any default by Tenant, such waiver shall
not be construed as a waiver of any covenant, condition or agreement set forth
in this Lease except as to the specific circumstances described in such written
waiver.

          (c) All rights and remedies of Tenant set forth herein are in addition
to all other rights and remedies available to Tenant hereunder or at law or in
equity. All rights and remedies available to Tenant hereunder or at law or in
equity are expressly declared to be cumulative. The exercise by Tenant of any
such right or remedy shall not prevent the concurrent or subsequent exercise of
any other right or remedy. No delay in the enforcement or exercise of any such
right or remedy shall constitute a waiver of any default by Landlord hereunder
or of any of Tenant's rights or remedies in connection therewith.

     19.4 (a) If Landlord shall institute proceedings against Tenant and a
compromise or settlement thereof shall be made, the same shall not constitute a
waiver of default or of any other covenant, condition or agreement set forth
herein, nor of any of Landlord's rights hereunder. Neither the payment by Tenant
of a lesser amount than the installments of annual base rent, additional rent or
of any sums due hereunder nor any endorsement or statement on a check or letter
accompanying a check for payment of rent or other sums payable hereunder shall
be deemed an accord and satisfaction, and Landlord may accept such check or
payment without prejudice to Landlord's right to recover the balance of such
rent or other sums or to pursue any other remedy available to Landlord. No
re-entry by Landlord, and no acceptance by Landlord of keys from Tenant, shall
be considered an acceptance of a surrender of this Lease.

          (b) If Tenant shall institute proceedings against Landlord and a
compromise or settlement thereof shall be made, the same shall not constitute a
waiver of default or of any other covenant, condition or agreement set forth
herein, nor of any of Tenant's rights hereunder. Neither the payment by Landlord
of a lesser amount than any sums due hereunder nor any endorsement or statement
on a check or letter accompanying a check for payment of sums payable hereunder
shall be deemed an accord and satisfaction, and Tenant may accept such check or
payment without prejudice to Tenant's right to recover the balance of such sums
or to pursue any other remedy available to Tenant.

     19.5 If Tenant defaults in the making of any payment or in the doing of any
act herein required to be made or done by Tenant, then Landlord, upon ten (10)
days prior written notice except in cases of emergency, may, but shall not be
required to, make such payment or do such


                                       54
<PAGE>   57

act. If Landlord elects to make such payment or do such act, all costs and
expenses incurred by Landlord, plus interest thereon at the rate per annum which
is two percent (2%) higher than the publicly announced "prime rate" then being
charged by Riggs National Bank of Washington, D.C., from the date paid by
Landlord to the date of payment thereof by Tenant, shall be immediately paid by
Tenant to Landlord; provided, however, that nothing contained herein shall be
construed as permitting Landlord to charge or receive interest in excess of the
maximum legal rate then allowed by law. The taking of such action by Landlord
shall not be considered as a cure of such default by Tenant or prevent Landlord
from pursuing any remedy it is otherwise entitled to in connection with such
default.

     19.6 If Tenant fails to make any payment of base rent or of additional rent
on or before the date such payment is due and payable, Tenant, shall pay to
Landlord a late charge of five percent (5%) of the amount of such payment;
provided, however, that Landlord shall waive such late fee the first two times
in each twelve (12) month period that Tenant fails to make a payment when due,
provided such payment is made before the expiration of the notice and cure
period set forth in Section 19.1(a). In addition, such payment shall bear
interest at the rate per annum which is two percent (2%) higher than the
publicly announced "prime rate" then being charged by Riggs National Bank of
Washington, D.C., from the date such payment became due to the date of payment
thereof by Tenant; provided, however, that nothing contained herein shall be
construed as permitting Landlord to charge or receive interest in excess of the
maximum legal rate then allowed by law. Such late charge and interest shall
constitute additional rent due and payable hereunder with the next installment
of annual base rent due hereunder.

     19.7 (a) Subject to the provisions of Section 21.3 hereof, Landlord shall
be in default under this Lease if Landlord fails to perform any covenant or
agreement to be performed by Landlord hereunder and either: (i) fails promptly
after written notice from Tenant to complete such cure within forty-five (45)
days after Tenant's notice or (ii) if such failure is of a type that cannot with
the exercise of reasonable diligence be cured within such forty-five (45) day
period, either fails promptly to commence its cure during such period or fails
thereafter to use commercially reasonable efforts to complete its cure as
promptly as possible.

          (b) Except as otherwise expressly limited in this Lease, in the event
a material default (as defined below) by Landlord occurs, upon written notice of
such material default to Landlord and to the holder (the "HOLDER") of any
mortgage, deed of trust, or other voluntary lien recorded against the Building
or the Complex, as Tenant's sole and exclusive remedy therefor (except where
another remedy is set forth herein), Tenant shall have the right to terminate
this Lease effective on the date specified in such notice, which date shall not
be not less than four (4) months and not more than one (1) year after the date
of such notice, provided that Landlord's default has not been cured prior to the
date on which Tenant has entered into a new lease. Tenant's notice to the holder
shall specify the nature of Landlord's default in detail, shall offer the holder
an opportunity to cure same, as provided in Section 21.3 hereof, and shall
specify that, in the event the holder fails to cure same, Tenant may exercise
its right to terminate this Lease. As used herein, the term "MATERIAL" means the
failure by Landlord to cure (or if not possible of cure to commence curing and
thereafter, to diligently pursue the cure of such material default within
forty-five (45) days after Landlord's receipt of Tenant's notice specifying in
reasonable detail such failure) a breach of Landlord's obligation under this
Lease which failure to cure affects in a


                                       55
<PAGE>   58

material,adverse way the ability of Tenant to use and occupy the Premises for
any of the purposes permitted hereunder or to exercise its material rights
hereunder.

     19.8 In the event that Landlord shall employ an attorney to enforce
Tenant's covenants and obligations under this Lease, whether or not Landlord
proceeds to recover possession or otherwise commence any other proceeding
against Tenant, Tenant shall be liable for all costs and expenses sustained by
Landlord in the enforcement of such covenants and obligations, including but not
limited to attorneys' fees and expenses, costs of collection and court costs.

                                   ARTICLE XX
                                   BANKRUPTCY

     20.1 The following shall be Events of Bankruptcy under this Lease:

          (a) Tenant's or any guarantor's becoming insolvent, as that term is
defined in Title 11 of the United States Code (the "BANKRUPTCY CODE") or under
the insolvency laws of any state, district, commonwealth or territory of the
United States (the "INSOLVENCY LAWS");

          (b) The appointment of a receiver or custodian for any or all of
Tenant's property or assets, or the institution of a foreclosure action upon any
of Tenant's or any guarantor's real or personal property;

          (c) The filing by Tenant of a voluntary petition under the provisions
of the Bankruptcy Code or Insolvency Laws;

          (d) The filing of an involuntary petition against Tenant or any
guarantor as the subject debtor under the Bankruptcy Code or Insolvency Laws,
which either (i) is not dismissed within one hundred twenty (120) days of
filing, or (ii) results in the issuance of an order for relief against the
debtor; or

          (e) Tenant's making or consenting to an assignment for the benefit of
creditors or a common law composition of creditors.

     20.2 (a) Upon occurrence of an Event of Bankruptcy, Landlord shall have all
rights and remedies available to Landlord pursuant to Article XIX, provided that
while a case in which Tenant is the subject debtor under the Bankruptcy Code is
pending and only for so long as Tenant or its Trustee in Bankruptcy (hereinafter
referred to as "TRUSTEE") is in compliance with the provisions of Section
20.2(b), (c) and (d) below, Landlord shall not exercise its rights and remedies
pursuant to Article XIX.

          (b) In the event Tenant becomes the subject debtor in a case pending
under the Bankruptcy Code, Landlord's right to terminate this Lease pursuant to
Section 20.2(a) shall be subject to the rights of Trustee to assume or assign
this Lease. Trustee shall not have the right to assume or assign this Lease
unless Trustee promptly (i) cures all defaults under this Lease, (ii)
compensates Landlord for monetary damages incurred as a result of such defaults
and (iii)


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<PAGE>   59

provides adequate assurance of future performance on the part of Tenant as
debtor in possession or on the part of the assignee tenant.

          (c) Landlord and Tenant hereby agree in advance that adequate
assurance of future performance, as used in Section 20.2(b) above, shall mean
that all of the following minimum criteria must be met: (i) Trustee must agree
that Tenant's business shall be conducted in a first-class manner, and that no
liquidating sales, auctions, or other non-first-class business operation shall
be conducted on the Premises; (ii) Trustee must agree that the use of the
Premises as stated in this Lease will remain unchanged and that no prohibited
use shall be permitted; (iii) Trustee must agree that the assumption or
assignment of this Lease will not violate or affect the rights of other tenants
in the Building; (iv) if the Security Deposit (whether in the form of cash or
Letter of Credit pursuant to Article V) is not immediately and readily
accessible for Landlord to apply pursuant to this Lease, Trustee must pay to
Landlord at the time the next monthly installment of annual base rent is due
under this Lease, in addition to such installment of annual base rent, an amount
equal to the monthly installments of annual base rent and additional rent due
under this Lease for the next six (6) months under this Lease, three (3) months
of said amount to be applied towards the next payments of rent or other
obligations due under this Lease and three (3) months of said amount to be held
by Landlord in escrow, without interest, until either Trustee or Tenant defaults
in its payment of rent or other obligations under this Lease (whereupon Landlord
shall have the right to draw on such escrowed funds) or until the expiration of
this Lease (whereupon the funds shall be returned to Trustee or Tenant); and (v)
Tenant or Trustee must agree to pay to Landlord at any time Landlord is
authorized to and does draw on the escrow account the amount necessary to
restore such escrow account to the original level required by Section
20.2(c)(iv).

          (d) In the event Tenant is unable to (i) cure its defaults, (ii)
reimburse the Landlord for its monetary damages, (iii) pay the rent due under
this Lease and all other payments required of Tenant under this Lease on time
(or within ten (10) days of the due date) or (iv) meet the criteria and
obligations imposed by Section 20.2(c) above, Tenant agrees in advance that (A)
it has not met its burden to provide reasonable assurance of prompt cure and
adequate assurance of future performance, (B) it has therefore failed to meet
the minimum requirement for assuming this Lease, and (C) this Lease may be
terminated by Landlord in accordance with Section 20.2(a) above.

                                   ARTICLE XXI
                                  SUBORDINATION

     21.1 This Lease is subject to and subordinate to the lien of any and all
mortgages (which term "MORTGAGES" shall include both construction and permanent
financing and shall include deeds of trust and similar security instruments)
which may now encumber the Building, and to any and all renewals, extensions,
modifications, recastings or refinancing thereof. Landlord represents to Tenant
that as of the date hereof, Wells Fargo, as defined below, is the only mortgage
holder encumbering the Building. Subject to Tenant's receipt of an SNDA in
accordance with Section 21.3(d) below, this Lease shall also be subject and
subordinate to the lien of (i) any new first mortgage that hereafter may
encumber the Building, and (ii) any second or junior mortgages that may
hereafter encumber the Building, provided the holder of the first


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<PAGE>   60

mortgage consents to such subordination. At any time after the execution of this
Lease, the holder of any mortgage to which this Lease is subordinate shall have
the right to declare this Lease to be superior to the lien of such mortgage, and
Tenant agrees to execute all documents required by such holder in confirmation
thereof.

     21.2 In confirmation of the foregoing subordination, Tenant shall, at
Landlord's request and subject to the provisions of Section 21.3(d) below,
promptly execute any requisite or appropriate certificate or other document. If
Tenant fails to execute and deliver the same "as is" or to respond in good faith
with reasonable comments within ten (10) business days after Landlord's request
therefor, and such failure to either execute and deliver or respond continues
for a period of three (3) business days following a second (2nd) notice thereof
from Landlord, Tenant shall pay Landlord as additional rent the sum of One
Thousand Dollars ($1,000) for each day after the tenth (10th) business day that
Tenant has not executed and delivered such certificate or document or otherwise
responded in good faith to Landlord's request therefor. Tenant agrees that in
the event any proceedings are brought for the foreclosure of any mortgage
encumbering the Building, Tenant shall attorn to the purchaser at such
foreclosure sale, provided that such purchaser or holder assumes the obligations
of Landlord under this Lease arising from and after the date of such transfer,
and Tenant shall recognize such purchaser as the landlord under this Lease, and
Tenant waives the provisions of any statute or rule of law, now or hereafter in
effect, which may give or purport to give Tenant any right to terminate or
otherwise adversely affect this Lease and the obligations of Tenant hereunder in
the event any such foreclosure proceeding is prosecuted or completed. Tenant
agrees that upon such attornment, such purchaser shall not (i) be bound by any
payment of annual base rent or additional rent for more than one (1) month in
advance, except accrued credits pursuant to Section 4.3 and prepayments in the
nature of security for the performance by Tenant of its obligations under this
Lease, but only to the extent such prepayments have been delivered to such
purchaser, (ii) be bound by any amendment of this Lease made without the consent
of any lender providing construction or permanent financing for the Building, if
such consent is required and unless such consent has been deemed to have been
received, (iii) be liable for damages for any act or omission of any prior
landlord; or (iv) be subject to any offsets or defenses which Tenant might have
against any prior landlord; provided, however, that after succeeding to
Landlord's interest under this Lease, such purchaser shall perform in accordance
with the terms of this Lease all obligations of Landlord arising after the date
such purchaser acquires title to the Building. Upon request by such purchaser,
Tenant shall execute and deliver an instrument or instruments confirming its
attornment.

     21.3 (a) After receiving notice from any person, firm or other entity that
it holds a mortgage, deed of trust or ground lease on the Building, or the land
on which the Building is situated, no notice from Tenant to Landlord alleging
any default by Landlord shall be effective unless and until a copy of the same
is given to such holder, trustee or ground lessor; provided, however, that
Tenant shall have been furnished with the name and address of such holder,
trustee or ground lessor. The curing of any of Landlord's defaults by such
holder, trustee or ground lessor shall be treated as performance by Landlord.

          (b) In addition to the time afforded the Landlord for the curing of
any default, any such holder, trustee, or ground lessor shall have such
additional time as may be necessary given the nature and extent of the default
(including such time as may be necessary in order to


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<PAGE>   61

foreclose the mortgage and obtain possession of the Land and Building) after the
expiration of the period allowed to the Landlord for the cure of any such
default within which to cure such default so long as any such holder, trustee or
ground lessor acts with reasonable diligence. Except as may otherwise be
provided in any other agreement between Tenant and the holder, trustee or ground
lessor, the additional cure period afforded such holder, trustee or ground
lessor shall be limited to an additional ninety (90) days, except that if such
default is of the type that with reasonable diligence such default cannot be
cured within such ninety (90) day period, then such holder, trustee or ground
lessor shall have such additional time to effect such cure, up to an additional
ninety (90) days, as may be reasonable under the circumstances.

          (c) In the event that any lender providing construction or permanent
financing or any refinancing for the Building requires, as a condition of such
financing, that modifications to this Lease be obtained, and provided that such
modifications (i) are reasonable, (ii) do not adversely affect Tenant's use and
occupancy of the Premises as herein permitted, (iii) do not increase the rent
and other sums to be paid by Tenant hereunder, (iv) do not reduce the services
provided to Tenant under this Lease, (v) do not decrease Landlord's obligations
under this Lease. (vi) do not materially affect the rights and obligations of
Tenant under this Lease and (vii) do not reduce or adversely affect in any way
Tenant's rights with respect to signage, renewal and expansion as set forth in
this Lease, Landlord may submit to Tenant a written amendment to this Lease
incorporating such required changes, and Tenant hereby covenants and agrees to
execute, acknowledge and deliver such amendment to Landlord within ten (10) days
of Tenant's receipt thereof.

          (d) Landlord, Tenant and Wells Fargo Bank, National Association
("Wells Fargo"), holder of the deed of trust secured by the Building, shall
enter into a subordination, non-disturbance and attornment agreement ("SNDA") in
the form attached hereto as Exhibit F and made a part hereof. Such SNDA shall be
delivered to Tenant promptly after the execution and delivery of this Lease and
all sums due hereunder by Tenant to Landlord. Landlord shall, at no cost to
Landlord, obtain from any future holder of any mortgage or deed of trust on the
Building an SNDA in substantially the same form attached hereto as Exhibit F.

                                  ARTICLE XXII
                                  HOLDING OVER

     22.1 In the event that Tenant shall not immediately surrender the Premises
on the date of the expiration of the Lease Term, Tenant shall become a tenant by
the month at a base rent and additional rent equal to one hundred twenty-five
percent (125%) of the amount of the annual base rent and all additional rent in
effect during the last month of the Lease Term (the "Holdover Rent") for up to
the first three (3) months of any such holdover period and for any holdover
period thereafter, the Holdover Rent shall be equal to one hundred fifty percent
(150%) of the amount of the annual base rent and all additional rent in effect
during the last month of the Lease Term. Said monthly tenancy shall commence on
the first day following the expiration of the Lease term. As a monthly tenant,
Tenant shall be subject to all the terms, conditions, covenants and agreements
of this Lease. Tenant shall give to Landlord at least thirty (30) days' written
notice of any intention to quit the Premises. Tenant shall be entitled to thirty
(30) days' written notice to quit the Premises, which notice shall not be given
until the expiration of the Lease


                                       59
<PAGE>   62

Term, unless Tenant is in monetary or other material non-monetary default under
the terms and provisions of this Lease beyond any applicable notice and cure
period, in which event Tenant shall not be entitled to any notice to quit, the
usual thirty (30) days' notice to quit being hereby expressly waived.
Notwithstanding the foregoing provisions of this Section 22.1, in the event that
Tenant shall hold over after the expiration of the Lease Term, and if Landlord
shall desire to regain possession of the Premises promptly at the expiration of
the Lease Term, then at any time prior to Landlord's acceptance of rent from
Tenant as a monthly tenant hereunder, Landlord, at its option may forthwith
re-enter and take possession of the Premises by any legal process in force in
the State of Maryland.

                                  ARTICLE XXIII
                              COVENANTS OF LANDLORD

     23.1 Landlord covenants that it has the right to make this Lease for the
term aforesaid, and that if Tenant shall pay all rent when due and punctually
perform all the covenants, terms, conditions and agreements of this Lease to be
performed by Tenant, Tenant shall, during the term hereby created, freely,
peaceably and quietly occupy and enjoy the full possession of the Premises
without molestation or hindrance by Landlord or any party claiming through or
under Landlord, subject to the provisions of Section 23.2 hereof. Tenant
acknowledges and agrees that its leasehold estate in and to the Premises vests
on the date this Lease is executed, notwithstanding that the term of this Lease
will not commence until a future date.

     23.2 Landlord hereby reserves to itself and its successors and assigns the
following rights (all of which are hereby consented to by Tenant): (i) to change
the street address or name of the Building, or the arrangement or location of
entrances, passageways, doors, doorways, corridors, elevators, stairs, toilets,
or other public parts of the Building, provided, however, Landlord shall not
voluntarily change the name of the Building to the name of a tenant in the
Building for so long as Tenant leases the entire initial Premises; (ii) to
erect, use and maintain pipes and conduits (such pipes and conduits to be
installed, at Landlord's option, above the ceiling, below the floor, concealed
or "boxed in") in and through the Premises, provided that any such change or
changes do not materially and adversely affect Tenant's ability to conduct its
business at the Premises or materially and adversely affect its access to or use
or enjoyment of the Premises; (iii) subject to Tenant's rights under this Lease,
to grant to anyone the exclusive right to conduct any particular legal business
or undertaking in the Building; and (iv) to grant anyone the exclusive right
from time to time on a temporary basis to use any portion of the common public
areas of the Building (provided same does not materially, adversely affect
Tenant's use of or access to the Premises or the parking deck and surface
parking areas appurtenant to the Building). Landlord may exercise any or all of
the foregoing rights without being deemed to be guilty of an eviction, actual or
constructive, or a disturbance or interruption of the business of Tenant or of
Tenant's use or occupancy of the Premises. If, as a result of Landlord's change
of street address or name of the Building, Tenant must replace its professional
stationery, Landlord agrees to reimburse Tenant, up to Ten Thousand Dollars
($10,000.00) based on invoices presented to Landlord, for the reasonable cost of
replacing stock on hand at the time of such change with stationery of equal
amount and quality.


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<PAGE>   63

                                  ARTICLE XXIV
                                     PARKING

     24.1 (a) During the Lease Term, upon the written request of Tenant received
by Landlord on or before the Lease Commencement Date, Landlord agrees to make
available to Tenant and its employees and to Tenant's permitted subtenants
monthly parking permits in an amount not to exceed 3.5 monthly parking permits
for each one thousand (1,000) square feet of rentable area in the Premises, as
they may be expanded during the Lease Term, for the parking of standard-sized
passenger automobiles, SUVs and minivans in the parking deck serving the
Building (the "PARKING DECK") and on the surface parking lot appurtenant to the
Building on a non-exclusive, unassigned, first-come, first-served basis. During
the first (1st) Lease Year, the charge for such permits shall be Fifty-Five
Dollars ($55.00) per month per permit. Thereafter, the charge for such permits
shall be the prevailing rate charged from time to time by Landlord or the
operator of the parking deck and surface parking areas; provided, however, that
in no event shall the cumulative annual increase in the charge for permits in
the parking deck and surface parking areas during any twelve (12) month period
exceed five percent (5%) of the aggregate amount of the charge for such permits
during the immediately preceding twelve (12) month period. Tenant also shall
have the right to negotiate directly with the operator of the parking deck and
the surface parking lot for additional parking permits. Notwithstanding the
foregoing, Landlord does not guarantee the availability of any such monthly
parking permits to Tenant following the first (1st) Lease Year if and to the
extent that Tenant does not purchase such monthly parking permits available to
it during the first (1st) Lease Year and thereafter continuously maintain such
permits.

          (b) Included among the parking permits described in subsection (a)
above, Landlord will provide Tenant with twenty-five (25) reserved parking
spaces in the parking deck adjacent to the Building (the "Reserved Parking
Spaces"). Landlord, at Tenant's expense, shall promptly install appropriate
"reserved parking" signage identifying the Reserved Parking Spaces as reserved
for Tenant. During the first (1st) Lease Year, the charge for such Reserved
Parking Spaces shall be One Hundred Ten Dollars ($110.00) per month per Reserved
Parking Space. Thereafter, the rate to be paid by Tenant for the Reserved
Parking Spaces shall be the prevailing monthly rate charged to other monthly
parking customers for reserved parking space at the Office Complex; provided,
however, that in no event shall the cumulative annual increase in the charge for
the Reserved Parking Spaces during any twelve (12) month period exceed five
percent (5%) of the aggregate amount of the charge for such Reserved Parking
Spaces during the immediately preceding twelve (12) month period. The location
of the Reserved Parking Spaces is shown on Exhibit H attached hereto and made a
part hereof. In the event Landlord or the operator of the parking deck and the
surface parking area determine to cause repairs to the parking deck and/or the
surface parking area, the temporary location of the Reserved Parking Spaces
shall be subject to the mutual agreement of Landlord and Tenant; which agreement
shall not be unreasonably withheld, conditioned or delayed. Promptly after the
completion of such repairs, the original Reserved Parking Spaces shall be
restored to Tenant's use. Landlord shall have no duty or obligation to enforce
the reserved parking provided to Tenant in this Section 25.1(b), such being the
responsibility of the operator of the parking deck and surface parking lot, and
Landlord shall not be liable to Tenant for any unauthorized vehicles which are
parking in


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such Reserved Parking Spaces. Tenant shall have no right to have any
unauthorized vehicle towed, moved or removed form the parking lot or such
Reserved Parking Spaces.

     24.2 It is understood and agreed that the parking deck will be operated on
a self-parking basis and that, other than the Reserved Parking Spaces, no
specific parking spaces will be allocated for use by Tenant. Landlord reserves
the right to institute a valet parking system or other parking controls, rules
or regulations, at any time and in its sole discretion. Each user of the parking
deck will have the right to park in any available parking space in accordance
with regulations of uniform applicability promulgated by Landlord or the parking
deck operator. Notwithstanding anything herein to the contrary, Landlord and the
operator of the parking deck and surface parking area hereby reserves the right
from time to time to designate any portion of the parking deck to be used
exclusively by visitors and retail patrons to the Building or other tenants;
provided that such designation does not decrease the number of monthly parking
permits available to Tenant below the ratio set forth in Section 24.1(a) above.

     24.3 Tenant agrees that it and its employees shall observe reasonable
safety precautions in the use of the parking deck and shall at all times abide
by all rules and regulations promulgated by Landlord or the parking deck
operator governing its use. Landlord reserves the right to require that an
identification or parking sticker shall be displayed at all times in all cars
parked in the parking deck. If such a parking sticker requirement shall be
instituted, any car not displaying such a sticker may be towed away at the car
owner's expense. In addition, Landlord's and Tenant's use of the parking deck
shall be subject to all applicable laws and regulations.

     24.4 The parking deck will remain open on Monday through Friday (excluding
legal holidays) during the normal hours of operation of the Building on such
days. Landlord reserves the right to close the parking deck and surface parking
areas during periods of unusually inclement weather or for repairs. At all times
when the parking deck or surface parking areas are closed, monthly permit
holders shall be afforded access to the parking deck by means of a magnetic card
or other procedure provided by Landlord or the parking deck operator and
provided further that any closures for repairs shall be for as short a period of
time as is reasonably feasible.

     24.5 It is understood and agreed that the Landlord does not assume any
responsibility for, and, subject to the last sentence of Section 15.1 above,
shall not be held liable for any damage or loss to any automobiles parked in the
parking deck or to any personal property located therein, or for any injury
sustained by any person in or about the parking deck. Notwithstanding the
preceding sentence, Landlord shall not be released from liability to Tenant for
any damage or injury to any automobiles or other vehicles parked in the parking
deck or the surface parking lot during normal hours of operation of the Building
as provided in Section 14.1 hereof, or to any personal property located therein
or thereon, caused directly by the willful misconduct or negligence of Landlord
or its employees; provided, however, in no event shall Landlord have any
liability to Tenant for any claims based on the interruption of or loss to
Tenant's business or for any indirect losses or consequential damages whatsoever
or for claims with respect to any property for which Tenant (or its employees)
are insured or required to be insured hereunder.


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                                   ARTICLE XXV
                               GENERAL PROVISIONS

     25.1 Tenant acknowledges that neither Landlord nor any broker, agent or
employee of Landlord has made any representations or promises with respect to
the Premises or the Building except as herein expressly set forth, and no
rights, privileges, easements or licenses are being acquired by Tenant except as
herein expressly set forth.

     25.2 Nothing contained in this Lease shall be construed as creating a
partnership or joint venture of or between Landlord and Tenant, or to create any
other relationship between the parties hereto other than that of landlord and
tenant.

     25.3 Landlord recognizes Transwestern Carey Winston and Julien J. Studley
as the brokers procuring this Lease and shall pay said brokers a commission
pursuant to a separate agreement between said brokers and Landlord. Landlord and
Tenant each represent and warrant to the other that, except as provided in the
preceding sentence, neither of them has employed or dealt with any broker, agent
or finder in carrying on the negotiations relating to this Lease. Tenant shall
indemnify and hold Landlord harmless from and against any claim or claims for
brokerage or other commissions asserted by any broker, agent or finder engaged
by Tenant or with whom Tenant has dealt in connection with this Lease, other
than the brokers named in the first sentence of this Section 25.3. Landlord
shall indemnify and hold Tenant harmless from and against any claim or claims
for brokerage or other commissions asserted by any broker, agent or finder
engaged by Landlord or with whom Landlord has dealt in connection with this
Lease.

     25.4 (a) Tenant agrees, at any time and from time to time, upon not less
than ten (10) days' prior written notice by Landlord, to execute, acknowledge
and deliver to Landlord a true statement in writing (i) certifying that this
Lease is unmodified and in full force and effect (or if there have been any
modifications, that the Lease is in full force and effect as modified and
stating the modifications), (ii) stating the dates to which the rent and any
other charges hereunder have been paid by Tenant, (iii) stating whether or not,
to the best knowledge of Tenant, Landlord is in default in the performance of
any covenant, agreement or condition contained in this Lease, and if so,
specifying the nature of such default, (iv) stating the address to which notices
to Tenant are to be sent, and (v) stating such other information as Landlord,
Wells Fargo or any other holder of a mortgage secured by the Building may
reasonably request with respect to the status of this Lease on such form as
Landlord, Wells Fargo or such holder may reasonably request. Any such statement
delivered by Tenant may be relied upon by any owner of the Building or the Land,
any prospective purchaser of the Building or the Land, any mortgagee or
prospective mortgagee of the Building or such Land or of Landlord's interest
therein, or any prospective assignee of any such mortgagee. If Tenant fails to
execute and deliver such statement as is or fails to provide Landlord with
reasonable comments with respect thereto within ten (10) business days after
Landlord's request therefor, and such failure to either execute and deliver such
statement or to respond with reasonable comments to Landlord's request continues
for a period of three (3) business days following a second (2nd) notice thereof
from Landlord, Tenant shall pay Landlord as additional rent the sum of One
Thousand Dollars ($1,000.00) for each day after the tenth (10th) business day
that Tenant has not executed and delivered such certificate or document or
provided Landlord with reasonable comments with respect thereto. Upon


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Landlord's written request, but not more than two (2) times in any twelve (12)
month period, Tenant shall deliver to Landlord Tenant's most recently audited
financial statements (or, if Tenant does not produce audited financial
statements in the ordinary course, such financial statements shall be certified
as true, complete and correct by Tenant's chief financial officer). Any
confidential or proprietary information about a party which is disclosed by one
party to the other party and is, at the time of disclosure, clearly identified
as confidential or proprietary information shall be used by the other party only
in fulfillment of its obligations hereunder and shall be held in confidence.
Notwithstanding any of the foregoing to the contrary, however, any party may (a)
discuss the substance of the information or any relevant details of the
transactions contemplated herein on a confidential basis with any of its
attorneys, accountants, professional consultants, financial advisors, rating
agencies, or potential lenders, as the case may be, and (b) disclose such
matters (including by issuance of a press release) as may be necessary or
appropriate to comply with applicable laws, including, without limitation, SEC
and other governmental regulatory, disclosure, tax and reporting requirements.

          (b) Landlord agrees upon not less than fifteen (15) business days'
prior written notice and not more than one (1) time in any twelve month period,
to execute, acknowledge and deliver to Tenant a true statement in writing (i)
certifying that this Lease is unmodified and in full force and effect (or if
there have been any modifications, that the Lease is in full force and effect as
modified and stating the modifications), (ii) stating the dates to which the
rent and any other charges hereunder have been paid by Tenant, (iii) stating
whether or not, to the best knowledge of Landlord, Tenant is in default in the
performance of any covenant, agreement or condition contained in this Lease, and
if so, specifying the nature of such default and (iv) stating the address to
which notices to Landlord are to be sent.

     25.5 Landlord and Tenant each hereby waive trial by jury in any action,
proceeding or counterclaim brought by either of them against the other in
connection with any matter arising out of or in any way connected with this
Lease, the relationship of landlord and tenant hereunder, Tenant's use or
occupancy of the Premises, or any claim of injury or damage.

     25.6 All notices or other communications required hereunder shall be in
writing and shall be deemed duly given if delivered in person (with receipt
therefor), or if sent by certified or registered mail, return receipt requested,
postage prepaid, or by recognized overnight courier, to the following addresses:
(i) if to Landlord at c/o Boston Properties, Inc., 401 9th Street, N.W., Suite
700, Washington, D.C. 20004, Attn: Debra G. Moses with a courtesy copy to Boston
Properties, Inc., Prudential Center, 800 Boylston Drive, Boston, Massachusetts
02199-8001, Attn: Legal Department; (ii) if to Tenant, at the Premises,
Attention: Vice President of Operations, with a courtesy copy to Douglas K.
Hirsch, Esq., Shulman, Rogers, Gandal, Pordy & Ecker, P.A., 11921 Rockville
Pike, Third Floor, Rockville, MD 20852-2743, (provided, however, that any
failure to provide such courtesy copy shall not in any way invalidate or
otherwise impair the delivery of such notice to Tenant), except that prior to
the Lease Commencement Date, notices to Tenant shall be sent to Tenant at 6701
Democracy Boulevard, Rockville, Maryland, 20817 such address as Tenant shall
designate and inform Landlord in accordance with this Section 25.6. Either party
may change its address for the giving of notices by notice given in accordance
with this Section.


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<PAGE>   67

     25.7 If any provision of this Lease or the application thereof to any
person or circumstance shall to any extent be invalid or unenforceable, the
remainder of this Lease, or the application of such provision to persons or
circumstances other than those as to which it is invalid or unenforceable, shall
not be affected thereby, and each provision of this Lease shall be valid and
enforceable to the fullest extent permitted by law.

     25.8 Feminine or neuter pronouns shall be substituted for those of the
masculine form, and the plural shall be substituted for the singular number, in
any place or places herein in which the context may require such substitution.

     25.9 The provisions of this Lease shall be binding upon, and shall inure to
the benefit of, the parties hereto and each of their respective representatives,
successors and assigns, subject to the provisions hereof restricting assignment
or subletting by Tenant.

     25.10 This Lease contains and embodies the entire agreement of the parties
hereto and supersedes all prior agreements, negotiations and discussions between
the parties hereto. Any representation, inducement or agreement that is not
contained in this Lease shall not be of any force or effect. This Lease may not
be modified or changed in whole or in part in any manner other than by an
instrument in writing duly signed by both parties hereto.

     25.11 This Lease shall be governed by and construed in accordance with the
laws of the State of Maryland, without regard to the conflicts of laws
principles.

     25.12 Article and section headings are used herein for the convenience of
reference and shall not be considered when construing or interpreting this
Lease.

     25.13 The submission of an unsigned copy of this document to Tenant for
Tenant's consideration does not constitute an offer to lease the Premises or an
option to or for the Premises. This document shall become effective and binding
only upon the execution and delivery of this Lease by both Landlord and Tenant.

     25.14 Time is of the essence of each provision of this Lease.

     25.15 This Lease shall not be recorded, except that upon the request of
either party, the parties agree to execute, in recordable form, a short-form
memorandum of this Lease, provided that such memorandum shall not contain any of
the specific rental terms set forth herein. Such memorandum may be recorded in
the land records of the State of Maryland, and the party desiring such
recordation shall pay all recordation costs. Not later than the last day of the
Term, the party who recorded the memorandum shall execute and record an
appropriate release of the memorandum.

     25.16 Except as otherwise provided in this Lease, any amounts (whether
referenced herein as "ADDITIONAL RENT" or "ADDITIONAL RENT") owed by Tenant to
Landlord, and any cost, expense, damage, or liability shall be paid by Tenant to
Landlord upon the later to occur of (i) twenty (20) days after the date Landlord
notifies Tenant of the amount of such additional rent or such cost, expense,
damage or liability, or (ii) the day the next monthly installment of annual


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<PAGE>   68

base rent is due. If any payment hereunder is due after the end of the Lease
Term, such additional rent or such cost, expense, damage or liability shall be
paid by Tenant to Landlord not later than twenty (20) days after Landlord
notifies Tenant of the amount of such additional rent or such cost, expense,
damage or liability.

     25.17 All of Tenant's duties and obligations hereunder, including but not
limited to Tenant's duties and obligations to pay annual base rent, additional
rent and the costs, expenses, damages and liabilities incurred by Landlord for
which Tenant is liable, shall survive the expiration or earlier termination of
this Lease for any reason whatsoever. Landlord's obligation to refund to Tenant
any security deposit or overpayment made by Tenant under this Lease, including
pursuant to Article IV or Article V shall likewise survive the expiration or
earlier termination of this Lease.

     25.18 In the event Landlord or Tenant is in any way delayed, interrupted or
prevented from performing any of its obligations under this Lease (except, with
respect to Tenant, its obligations to pay Base Rent and additional rent
hereunder, payment of insurance premiums required to maintain Tenant's required
insurance coverage in effect at all times and its payment obligations under
Exhibit B), and such delay, interruption or prevention is due to fire, act of
God, governmental act, action or inaction (including, without limitation,
government delays in issuing any required building, construction, occupancy or
other permit, certificate or approval or performing any inspection or review in
connection therewith) strike, labor dispute, inability to procure materials, or
any other cause beyond Landlord's reasonable control (whether similar or
dissimilar), then (except as expressly set forth above with respect to Tenant)
Landlord or Tenant, as the case may be, shall be excused from performing the
affected obligations for the period of such delay, interruption or prevention.
The provisions of this Section 25.18 shall not apply to the time frames set
forth in Sections 2.4(b) and (c) with respect to Tenant's right to terminate
this Lease in the event the Anticipated Date of Substantial Completion is
delayed beyond the dates set forth therein.

     25.19 Tenant hereby represents and warrants to Landlord that all necessary
action has been taken to enter this Lease and that the person signing this Lease
on behalf of Tenant has been duly authorized to do so.

     25.20 This Lease shall be subject to and contingent upon Landlord's
receiving the approval of all of the terms and conditions contained herein by
Wells Fargo. Landlord agrees to use its reasonable efforts to secure such
approval. If such approval cannot be obtained, Landlord shall so notify Tenant,
Landlord shall return to Tenant the first month's rent and security deposit
delivered to Landlord pursuant to Sections 3.1 and 5.1 respectively and this
Lease shall terminate and all rights, obligations and liabilities of the parties
hereunder shall be released and discharged. Landlord shall notify Tenant no more
than fifteen (15) business days after the date on which Tenant delivers to
Landlord a fully executed copy of this Lease and all amounts then due to
Landlord hereunder whether Wells Fargo has approved or disapproved this Lease.
If Wells Fargo has not approved this Lease by the expiration of such fifteen
(15) business day period, then this Lease shall be deemed approved.


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<PAGE>   69

     25.21 Landlord and Tenant each hereby covenant and agree that each and
every provision of this Lease has been jointly and mutually negotiated and
authorized by both Landlord and Tenant; and, in the event of any dispute arising
out of any provision of this Lease, Landlord and Tenant do hereby waive any
claim of authorship against the other party.

     25.22 [Intentionally Deleted]

     25.23 The term "DAYS," as used herein, shall mean actual days occurring,
including, Saturdays, Sundays and holidays. The term "BUSINESS DAYS" shall mean
days other than Saturdays, Sundays and holidays. If any item must be
accomplished or delivered hereunder on a day that it is not a business day, it
shall be deemed to have been timely accomplished or delivered if accomplished or
delivered on the next following business day.

     25.24 Landlord agrees that (i) no officer, director, employee, shareholder
or partner of OTG Software, Inc. (each a "Partner of Tenant") shall have any
personal liability for the performance of any obligation under this Lease or any
covenant or agreement contained herein or any unpaid amount due hereunder, nor
shall any judgment be sought or obtained against any Partner of Tenant and
Landlord will not seek to obtain or impose any lien or charging order or claim
against any assets of any Partner of Tenant, (ii) in the event that Landlord is
awarded a money judgment against OTG Software, Inc., Landlord's sole recourse
for satisfaction of such judgment shall be limited to the assets of OTG
Software, Inc. and (iii) in no event shall the personal assets of any Partner of
Tenant be available to satisfy any judgment which Landlord may have against OTG
Software, Inc.

     25.25 This Lease includes and incorporates Rider No. 1 and Exhibits A, B,
C, D, E, F, G and H to the Lease.

                                  ARTICLE XXVI
                             ROOFTOP COMMUNICATIONS

     26.1 (a) Subject to the satisfaction, in Landlord's reasonable judgment, of
all of the conditions set forth in this Article, Tenant, at Tenant's sole cost
and expense, may install and maintain at least two (2) satellite dishes and/or
antennas (each individually referred to herein as a "Satellite Dish" and
collectively the "Satellite Dishes") on the roof of the Building for use in
connection with Tenant's business in the Premises. Notwithstanding anything in
this Article to the contrary, Tenant shall not be permitted to install a
Satellite Dish unless (I) Landlord, at Tenant's expense, determines, with
respect to the second (2nd) and any additional Satellite Dish, that there is
room on the Building for the Satellite Dish and that Tenant's Satellite Dish
shall not interfere with any other satellite dish or antenna of any other tenant
in the Building, (II) such Satellite Dish conforms to the specifications and
requirements set forth in the drawings and specifications prepared by a licensed
professional (the "Satellite Dish Drawings"), which Satellite Dish Drawings
shall be subject to the prior written approval of Landlord, which approval shall
not be unreasonably withheld, conditioned or delayed, (III) Landlord approves,
which approval shall not be unreasonably withheld, conditioned or delayed, the
size, capacity, power, location and proposed placement of such Satellite Dish,
and (IV) Tenant obtains, at its sole cost and expense, and provides copies to
Landlord of all necessary governmental permits


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<PAGE>   70

and approvals, including, without limitation, special exception permits, if
applicable, for the installation of the Satellite Dish equipment upon the
Building. Tenant, at Landlord's discretion, shall cause the Satellite Dish to be
painted in a nonmetallic paint to match the materials on the penthouse. In
addition, if the installation of the Satellite Dish on the roof of the Building
would penetrate the roof of the Building, then Tenant shall not be permitted to
install the Satellite Dish unless Tenant warrants and guaranties the roof to the
extent that Landlord will lose its existing roof warranty or guaranty and unless
Landlord approves, in writing, any such effect on the Building's structure or
service systems or any such structural alteration, which approval may be granted
or withheld by Landlord in its sole discretion. The Satellite Dish shall be
installed by a contractor reasonably acceptable to both Landlord and Tenant and
thereafter shall be properly maintained by Tenant, all at Tenant's sole expense.
At the expiration or earlier termination of the Lease Term, the Satellite Dish
shall be removed from the roof of the Building at Tenant's sole cost and expense
and that portion of the roof of the Building that has been affected by the
Satellite Dish shall be returned to the condition it was in prior to the
installation of the Satellite Dish. Tenant shall pay all subscription fees,
usage charges and hookup and disconnection fees associated with Tenant's use of
the Satellite Dish and Landlord shall have no liability therefor. All of the
provisions of this Lease, including, without limitation, the insurance,
maintenance, repair, release and indemnification provisions shall apply and be
applicable to Tenant's installation, operation, maintenance and removal of the
Satellite Dish.

          (b) Upon Tenant's satisfaction of the conditions set forth in Section
26.1(a) I-IV above, Landlord shall provide Tenant with space on the roof of the
Building, in a mutually agreeable location, for the installation of two (2)
standard and customary sized satellite dishes. Landlord agrees that it shall not
grant tenants who execute Leases for space in the Building after the date of
this Lease the right to install antennas, dishes or other equipment on the roof
of the Building which would, after consultation with Tenant, materially and
adversely interfere with the two Satellite Dishes described in the preceding
sentence. Tenant recognizes, however, that Tenant's rights to use the roof of
the Building are non-exclusive. Landlord agrees that if, after the date of this
Lease, any other tenant in the Building or any other entity that has the right
to use the roof of the Building (each a "Rooftop Rights Tenant") notifies
Landlord of its desire to place an antenna, dish or other equipment on the roof
of the Building and Tenant has satisfied the conditions set forth in Section
26.1(a) I-IV above, Landlord shall notify Tenant (a "Rooftop Notice") of such
request and with such notice shall provide Tenant with any information then
available to Landlord regarding the antenna, dish or equipment which such
Rooftop Rights Tenant desires to install on the roof of the Building. Tenant
shall notify Landlord ("Tenant's Rooftop Notice") within ten (10) days after its
receipt of a Rooftop Notice whether Tenant believes that the antenna, dish or
equipment which such Rooftop Rights Tenant desires to place on the roof of the
Building would materially and adversely impact the performance of Tenant's
Satellite Dishes. Tenant's Rooftop Notice shall state in reasonable detail the
reasons, if any, why and how the antenna, dish or equipment which the Rooftop
Rights Tenant desires to place on the roof of the Building would interfere with
the Satellite Dishes and offer reasonable alternative(s) to the placement of
such Rooftop Rights Tenant's antenna, dish or equipment. Landlord and Tenant
shall work with any Rooftop Rights Tenant in determining an acceptable location
for such Rooftop Rights Tenant's antenna, dish or other equipment. Except as
otherwise provided herein, nothing in this Section 26.1(b) shall restrict
Landlord's rights to allow other tenants in the Complex or other entities with
whom Landlord or its affiliates may contract, license or otherwise


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<PAGE>   71

agree to install, use, maintain, repair, operate, repair or remove any antenna,
dish or other equipment on or from the roof of the Building.

          (c) Except as shown on the Satellite Dish Drawings, as reasonably
approved by Landlord, Tenant shall not make any modification to the design,
structure or systems of the Building, required in connection with the
installation of the Satellite Dish without Landlord's prior written approval of
such modification and the plans therefor, which approval shall not be
unreasonably withheld, conditioned or delayed. The preceding sentence
notwithstanding, Landlord acknowledges and agrees that Tenant may use the
conduits connecting the Premises to the roof of the Building in conjunction with
the installation of the Satellite Dish on the roof of the Building and the
connection of the Satellite Dish to the Premises for use in Tenant's business.
Tenant agrees that, in addition to any indemnification provided Landlord in this
Lease, Tenant shall indemnify and shall hold Landlord and Boston Properties,
Inc., Landlord's managing agent, and their employees, shareholders, partners,
officers and directors, harmless from and against all costs, damages, claims,
liabilities and expenses (including attorney's fees and any costs of litigation)
suffered by or claimed against Landlord, directly or indirectly, based on,
arising out of or resulting from Tenant's use of the Satellite Dish and/or the
conduits to connect the Premises to the Satellite Dish. In addition, Tenant
shall be liable to Landlord for any actual damages suffered by Landlord or any
other tenant or occupant of the Building for any cessation or shortages of
electrical power or any other systems failure arising from Tenant's use of the
conduits to connect the Premises to the Satellite Dish.

          (d) Tenant, at its sole cost and expense, shall secure all necessary
permits and approvals from all applicable governmental agencies with respect to
the size, placement and installation of the Satellite Dish. In the event Tenant
is unable to obtain the necessary approvals and permits from any applicable
federal, state, county or other local governing authorities for the Satellite
Dish, Tenant shall have no remedy, claim, cause of action or recourse against
Landlord, nor shall such failure or inability to obtain any necessary permits or
approvals provide Tenant the opportunity to terminate this Lease.

          (e) Landlord makes no representations or warranties concerning the
suitability of the roof of the Building for the installation operation,
maintenance and repair of the Satellite Dish, Tenant having satisfied itself
concerning such matters.

          (f) Except in the event of emergency (in which case Tenant shall
notify Landlord thereof as soon as possible), Tenant shall not have access to
the Satellite Dish without Landlord's prior written consent, which consent shall
be granted to the extent necessary for Tenant to perform its maintenance
obligations hereunder only and only if Tenant is accompanied by Landlord's
representative (if Landlord so requests). Any such access by Tenant shall be
subject to reasonable rules and regulations relating thereto established from
time to time by Landlord, including without limitation rules and regulations
prohibiting such access unless Tenant is accompanied by Landlord's
representative and Tenant's agreement to reimburse Landlord for actual costs
incurred by Landlord to make Landlord's representative available to accompany
Tenant if after normal business hours.


                                       69
<PAGE>   72

          (g) Upon at least thirty (30) days' prior written notice to Tenant,
Landlord shall have the right to require Tenant to relocate a Satellite Dish, if
in Landlord's opinion such relocation is necessary in connection with the
maintenance and operation of the Building. Any such relocation shall be
performed by Tenant at Landlord's expense, and in accordance with all of the
requirements of this Section. Nothing in this Section shall be construed as
granting Tenant any line of sight easement with respect to such satellite dish
antenna; provided, however, that if Landlord requires that such antenna be
relocated in accordance with the preceding two (2) sentences, then Landlord
shall provide either (a) the same line of sight for such antenna as was
available prior to such relocation, or (b) a line of sight for such antenna
which is functionally equivalent to that available prior to such relocation.

          (h) It is expressly understood that by granting Tenant the right
hereunder, Landlord makes no representation as to the legality of such antenna
or its installation. In the event that any federal, state, county, regulatory or
other authority requires the removal or relocation of such antenna, Tenant shall
remove or relocate such antenna at Tenant's sole cost and expense, and Landlord
shall under no circumstances be liable to Tenant therefor.

          (i) The antenna may be used by Tenant only in the conduct of Tenant's
customary business in the Premises and Tenant's subtenants may share in the use
of Tenant's Satellite Dishes. Except as expressly provided in the preceding
sentence, no assignee or subtenant (other than an Affiliate of Tenant or a
Parent of Tenant or an assignee permitted or approved in accordance with the
provisions of Article VII hereof) shall have any rights pursuant to this
Article.

     26.2 Tenant shall maintain such insurance as is appropriate with respect to
the installation, operation and maintenance of the antenna. Landlord shall have
no liability on account of any damage to or interference with the operation of
the antenna except for physical damage caused by Landlord's gross negligence or
willful misconduct and Landlord expressly makes no representations or warranties
with respect to the capacity for an antenna placed on the roof of the Building
to receive or transmit signals. The operation of the antenna shall be at
Tenant's sole and absolute risk. Tenant shall in no event interfere with the use
of any other communications equipment located on the roof of the Building prior
to the installation of Tenant's antenna, or any such equipment thereafter
installed by Landlord in connection with operation of the Building.

     26.3 During any period that a Satellite Dish is located on the roof of the
Building, Tenant shall pay as additional rent to Landlord with respect to each
such Satellite Dish, commencing on the first day of the month that such
Satellite Dish is on the roof of the Building and on the first day of each month
thereafter, a monthly fee (the "Satellite Dish Charge") of Two Hundred Dollars
($200.00) per Satellite Dish, which monthly fee shall be paid along with the
base rent in accordance with Section 3.1 of this Lease. Such monthly fee for any
period less than a month shall be apportioned based upon the number of days in
that month. On the first day of each Lease Year after placement of the Satellite
Dish on the roof, the Satellite Dish Charge shall be increased to equal the
product of the Satellite Dish Charge in effect during the immediately preceding
Lease Year multiplied by 103%.


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                                  ARTICLE XXVII
                              RIGHT OF FIRST OFFER

     27.1 Landlord agrees that during the first seven (7) Lease Years of the
initial Lease Term with respect to the first and second floors of the Building
and during the first five (5) Lease Years of the initial Lease Term with respect
to the balance of the Building, Tenant shall have the right, at any time and
from time to time during the Lease Term, to lease additional space in the
Building which is contiguous to the Premises (the "Additional Space") as it
becomes available following the vacation of such leased space by the then
current tenant of such space, subject to the following terms and conditions:

          (a) Landlord shall notify Tenant of the availability of the Additional
Space.

          (b) In the event Tenant leases Additional Space during the first (1st)
Lease Year of the Lease Term, the annual base rent and additional rent with
respect to the Additional Space shall be the same amount per square foot and
shall be adjusted at the same time and in the same manner as the adjusted annual
base rent and additional rent then in effect with respect to the original
Premises. Thereafter, the annual base rent and additional rent with respect to
the Additional Space shall be one hundred percent (100%) of the then prevailing
fair market rent and additional rent attributable to Operating Expenses for the
Additional Space.

          (c) (i) For a period of ten (10) business days after receipt of any
such notice from Landlord, Tenant shall have the right to lease the Additional
Space from Landlord upon the terms and conditions set forth in this Lease (but
without any obligation on the part of Landlord to construct, alter, renovate,
repaint, recarpet or provide any construction allowance for tenant improvements
in the Additional Space, except as provided in subsection (e) below) commencing
on the date the Additional Space becomes available as set forth in the notice
from Landlord. In the event Tenant agrees to lease the Additional Space within
such ten (10) business day period, Landlord and Tenant shall promptly execute an
amendment to the Lease indicating the location and configuration of the
Additional Space. The number of square feet of rentable area of the Additional
Space shall be measured and calculated by Landlord's architect in accordance
with the provisions of Section 1.3 above and shall be set forth in the amendment
to the Lease.

              (ii) In the event the Additional Space identified by Landlord
comprises more than one (1) full floor in the Building Tenant may elect to lease
a portion of the Additional Space on a floor by floor basis. If Tenant desires
to lease less than all of the Additional Space available, Tenant shall notify
Landlord, within five (5) business days of Tenant's receipt of the notice
provided for in Section 27.1(a) above, of that portion of the Additional Space
which Tenant desires to lease from Landlord (the "Modified Additional Space").
In the event Tenant timely provides such notice to Landlord, Landlord and Tenant
shall proceed diligently and in good faith to amend this Lease to incorporate
the Additional Space or the Modified Additional Space, as the case may be.

          (d) Except as provided in subsection (c)(ii) above, in no event shall
Tenant have the right to lease less than all of the Additional Space available.


                                       71
<PAGE>   74

          (e) Tenant shall accept the Additional Space or the Modified
Additional Space, as the case may be, in "as is" condition; provided, however,
that in lieu of the Tenant Improvement Allowance described in the Work Agreement
attached hereto, Landlord agrees that it will provide Tenant with a construction
allowance (the "Additional Improvement Allowance") in an amount equal to the
product of (i) Thirty Dollars ($30.00) multiplied by (ii) the number of square
feet of rentable area in the Additional Space or the Modified Additional Space,
as the case may be, multiplied by (iii) a fraction the numerator of which is the
number of full calendar months in the period commencing on the commencement date
of the lease of the Additional Space or the Modified Additional Space, as the
case may be and continuing through the expiration of the Lease Term, exclusive
of any renewal term, and the denominator of which is one hundred twenty (120)
(the number of calendar months in the initial Lease Term). All work performed in
the Additional Space or the Modified Additional Space, as the case may be, shall
be performed in accordance with the terms and provisions of this Lease.

          (f) Tenant shall be obligated to pay additional rent with respect to
the Additional Space or the Modified Additional Space, as the case may be, in
accordance with the provisions of Article IV of this Lease or as otherwise
adjusted in the process set forth in Section 27.1(b) above.

          (g) In the event Tenant does not agree to lease the Additional Space
or the Modified Additional Space, as the case may be, within the applicable time
period specified in Section 27.1(c) above or if Tenant fails to timely notify
Landlord of its election to lease the Additional Space or the Modified
Additional Space, as the case may be, Landlord shall have the right to lease
such space to any other person or entity upon any terms and conditions which
Landlord desires, in its discretion.

          (h) The term of the lease for such Additional Space or the Modified
Additional Space, as the case may be, shall be for a period of not less than one
(1) year and, if there is more than one (1) year remaining in the Lease Term,
shall be coincident with the remaining Lease Term (subject to Tenant's right to
renew such term) under the Lease.

     27.2 If Tenant is in default under the Lease beyond any applicable notice
and cure period, on the date Landlord's notice is given to Tenant by Landlord or
at any time thereafter but prior to the commencement of the term for such
Additional Space or the Modified Additional Space, as the case may be, and if
such default is not cured within the applicable notice and cure period, if any,
provided in this Lease, then, at Landlord's option, Tenant's right to lease the
Additional Space or the Modified Additional Space, as the case may be, on such
occasion, shall lapse and be of no further force or effect.

     27.3 Tenant's right under this Article XXVII are subject to Landlord's
obligation to extend or renew the lease of the then current tenant of such space
beyond the expiration date of such tenant's lease upon any terms and conditions
to which Landlord and such tenant may agree.

     27.4 Tenant's right under this Article XXVII are personal to OTG Software,
Inc. and may be exercised only by OTG Software, Inc. and any assignee of OTG
Software, Inc. permitted


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<PAGE>   75

or approved by Landlord in accordance with the provision of Article VII hereof
and shall not be exercisable by any other assignee or subtenant.

     27.5 OTG Software, Inc. shall not be entitled to exercise its rights under
this Article XXVII to lease any Additional Space if at the time Tenant would
otherwise be entitled to exercise its rights, OTG Software, Inc. (together with
any of its subcontractors working in the Premises) is occupying less than fifty
percent (50%) of the Premises.

     IN WITNESS WHEREOF, Landlord and Tenant have executed this Lease under seal
on or as of the day and year first above written.

                                   LANDLORD:

                                   BOSTON PROPERTIES LIMITED PARTNERSHIP,
                                   a Delaware limited partnership

                                   By: BOSTON PROPERTIES, INC., a Delaware
                                       corporation, its sole general partner

                                       By: /s/ Raymond A. Ritchey        [SEAL]
                                           ------------------------------
                                       Name:   Raymond A. Ritchey
                                            -----------------------------
                                       Title:  Executive Vice President
                                             ----------------------------

WITNESS:                           TENANT:

                                   OTG SOFTWARE, INC.-, a Delaware corporation

By:   /s/ Gary J. Stein            By: /s/ Richard A. Kay
   -------------------------           ----------------------------------
Name:     Gary J. Stein            Name:   Richard A. Kay
     -----------------------            ---------------------------------
[CORPORATE SEAL]                   Title:  President, Chairman and Chief
                                           Executive Officer
                                         --------------------------------



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<PAGE>   76

                                   RIDER NO. 1

     THIS RIDER NO. 1 is attached to and made a part of that certain Office
Lease dated June 27, 2000 (the "LEASE"), by and between BOSTON PROPERTIES
LIMITED PARTNERSHIP ("LANDLORD") and OTG SOFTWARE, INC., a Delaware corporation
("TENANT"). The terms used in this Rider which are defined in the Lease have the
same meanings as provided in the Lease.

     WITNESSETH, that for and in consideration of Tenant's entering into the
Office Lease described above, and other good and valuable consideration, and
intending to be legally bound hereby, Landlord hereby grants to Tenant the right
to renew the initial term of the Lease upon the following terms and conditions:

     1. Landlord hereby grants to Tenant the conditional right, exercisable at
Tenant's option, to renew the term of the Lease for two (2) additional terms of
five (5) years each. If exercised and if the conditions applicable thereto have
been satisfied, each renewal term (a "RENEWAL TERM") shall commence immediately
following the end of the term then ending. The right of renewal herein granted
to Tenant shall be subject to, and shall be exercised in accordance with, the
following terms and conditions:

        (a) Tenant shall exercise its right of renewal with respect to each
Renewal Term by giving Landlord written notice of the exercise thereof (the
"RENEWAL OPTION NOTICE") not less than twelve (12) months and not more than
fifteen (15) months prior to the expiration of the term of the Lease then
ending. In the event that a renewal option notice is not given in a timely
manner, Tenant's right of renewal with respect to the Renewal Term and any
subsequent Renewal Term shall lapse and be of no further force or effect. If
Tenant is in default under the Lease, beyond any applicable notice and cure
period, on the date the renewal option notice is given or any time thereafter,
beyond any applicable notice and cure period, on or before the commencement date
of the Renewal Term, then, at Landlord's option, the renewal option notice shall
be totally ineffective and Tenant's right of renewal as to the Renewal Term and
any subsequent Renewal Term shall lapse and be of no further force of effect.

        (b) Promptly following Landlord's timely receipt of the renewal option
notice for a Renewal Term, Landlord and Tenant shall commence negotiations
concerning the amount of annual base rent which shall be payable during each
year of such Renewal Term and the Lease security, if any, that may be required,
it being intended that such annual base rent and pass throughs of Operating
Expenses shall be equal to the then prevailing fair market rent and pass
throughs of Operating Expenses for the Premises on the date the Renewal Term is
to commence. The parties shall have thirty (30) days after Landlord's receipt of
the renewal option notice in which to agree on the annual base rent which shall
be payable during each year of such Renewal Term and the Lease security, if any,
that may be required. The parties shall be obligated to conduct such
negotiations in good faith. Among the factors to be considered by the parties
during such negotiations shall be (i) the general office rental market in the
North Bethesda/Rockville, Maryland area, (ii) rental rates and security then
being obtained (or quoted if comparables are not readily available) by other
building owners for office buildings of


                                       -1-
<PAGE>   77

comparable size, location and quality to the Building in the North
Bethesda/Rockville, Maryland area, (iii) the rental rates and security then
being obtained by Landlord for comparable office space, in "as is" condition, in
the Building, (iv) escalations and pass-throughs of Operating Expenses as
provided in the Lease and then being obtained (or quoted if comparables are not
readily available) by other building owners for office buildings of comparable
size, location and quality to the Building in the North Bethesda/Rockville,
Maryland area, (v) concession packages then being obtained (or offered if
comparables are not readily available) by building owners for office buildings
in the North Bethesda/Rockville, Maryland area of comparable size, location and
quality to the Building, (vi) the location of the Premises within the Building
and (vii) whether a security deposit shall be required. All determinations of
fair market rent, escalations, security and pass-throughs of Operating Expenses
shall reflect market conditions expected to exist as of the date base rent based
on fair market rent is to commence, including, base rents and escalations,
rental abatements, construction allowances and other tenant concessions,
brokerage fees and other terms expected to be agreed to in market leases entered
into at such time; the determination of fair market rent shall reflect any
concessions that are not being granted to Tenant and whether brokerage fees are
being paid in connection with such renewal. If the parties agree on the base
rent payable during each year of a Renewal Term, they shall promptly execute an
amendment to the Lease stating the rent so agreed upon.

        (c) If, during such thirty (30) day period referred to in subparagraph
(b) above, the parties are unable to agree on the base rent payable during the
applicable Renewal Term, then Tenant shall have the option either (i) to rescind
its renewal option notice or (ii) to agree that the fair market rent shall be
determined in accordance with the procedure set forth in this subparagraph (c).
Tenant shall exercise its option by giving Landlord written notice of its
election within ten (10) days of the termination of the thirty (30) day period
provided for in subparagraph (b) above. If Tenant elects to rescind its renewal
option notice, Tenant's right to renew the term of the Lease and all subsequent
Renewal Terms shall lapse and be of no further force or effect. If Tenant shall
fail to notify Landlord of its election to rescind its renewal option notice,
Tenant shall be deemed to have elected not to rescind its renewal option notice.
If Tenant shall elect to proceed or shall be deemed to have elected to proceed
with the appraisal procedure provided in this subparagraph (c) then, within ten
(10) days after Landlord's receipt of Tenant's election to proceed with the
broker determination procedure or ten (10) days after the date on which Tenant
has been deemed to have elected to proceed with the broker determination
procedure, the parties shall appoint an independent, unaffiliated broker who
shall be mutually agreeable to both Landlord and Tenant, shall have at least ten
(10) years relevant experience and shall be knowledgeable in office rentals in
the North Bethesda/Rockville, Maryland market. If the parties are unable to
agree on an broker within such ten (10) day period, then each party, within five
(5) days after the expiration of the aforesaid ten (10) day period, shall
appoint an independent, unaffiliated broker (with the same qualifications) and
the two (2) brokers shall together appoint a third broker with the same
qualifications. The broker or brokers so appointed then shall determine, within
sixty (60) days after the appointment of such broker or brokers, the then fair
market base rent for the Premises. Among the factors to be considered by the
broker(s) in determining the fair market base rent for the Premises shall be
those factors set out in subparagraph (b) above. The figure arrived at by the
broker (or the average of the figures arrived at by the three brokers, if
applicable) shall be used as the fair market base rent for such renewal term. If
the three broker method is chosen, then if any broker's estimate of fair market
base rent


                                       -2-
<PAGE>   78

is either (x) less than ninety percent (90%) of the average figure or (y) more
than one hundred ten percent (110%) of such average, then the fair market rent
will be either (1) the average of the remaining two (2) appraisal figures
falling within such a range of percentages, (2) the remaining appraisal which is
within such range of percentages or (3) if none of the figures are within such
range, the average of the three (3) determinations. Landlord and Tenant shall
each bear the cost of its broker and shall share equally the cost of the third
broker.

        (d) During each Renewal Term, all the terms, conditions, covenants and
agreements set forth in the Lease shall continue to apply and be binding upon
Landlord and Tenant, except that (i) the annual base rent and any escalations
thereof payable during each year of a Renewal Term shall be the amount agreed
upon by Landlord and Tenant in the manner provided in Paragraphs 1(b) and (c)
above, and (ii) in no event shall Tenant have the right to renew the term of the
Lease, or any renewal term thereof, beyond the expiration of the second Renewal
Term, and (iii) no abatements, allowances or other concessions shall apply
during either Renewal Term, except to the extent otherwise agreed to by the
parties in accordance with this Rider.

     2. Tenant's rights under this Rider No. 1 are personal to and may be
exercised only by OTG Software, Inc. and any assignee of OTG Software, Inc.
permitted or approved by Landlord in accordance with the provision of Article
VII of the Lease.

     3. Tenant shall not be entitled to renew the Term of this Lease if, at the
time Tenant would otherwise be entitled to exercise its rights of renewal,
Tenant has assigned this Lease other than to an assignee permitted or approved
in accordance with the provisions of Article VII of the Lease or has subleased
fifty percent (50%) or more of the Premises.

Initials of:

/s/ RAR
------------------------
Landlord

/s/ RAK
------------------------
Tenant


                                      -3-
<PAGE>   79
                                    EXHIBIT A

                                   FLOORPLANS

[Exhibit A consists of four drawings, each drawing 8 1/2" by 11", that provides
general information related to the first, second, third and fourth floors of The
Preserve at Tower Oaks]


<PAGE>   80

                                    EXHIBIT B

                                 WORK AGREEMENT

         This Exhibit B is attached to and made a part of that certain Lease
Agreement dated as of June 27, 2000 (the "LEASE"), between BOSTON PROPERTIES
LIMITED PARTNERSHIP ("LANDLORD") and OTG SOFTWARE, INC. ("TENANT").

         1. Authorized Representatives. Tenant designates Patricia Akstin
("TENANT'S AUTHORIZED REPRESENTATIVE") as the person authorized to approve in
writing all plans, drawings, specifications, change orders, charges and
approvals pursuant to this Exhibit (and if Tenant appoints more than one
Tenant's Authorized Representative, then the act of one of such persons shall be
sufficient to bind Tenant). Tenant may designate a substitute Tenant's
Authorized Representative by written notice to Landlord. Landlord shall not be
obligated to respond to any instructions, approvals, changes, or other
communications from anyone claiming to act on Tenant's behalf other than
Tenant's Authorized Representative. All references in this Exhibit to actions
taken, approvals granted, or submissions made by Tenant shall mean that such
actions, approvals or submissions have been taken, granted or made, in writing,
by Tenant's Authorized Representative acting for Tenant.

         2. Landlord's Work. Landlord shall construct, furnish, install and
complete, in a good and workmanlike manner, using new materials, the
base-building core and shell (the "BASE BUILDING WORK," which shall be completed
in accordance with all applicable building code requirements), the parking deck,
parking area and site work associated with the Building (the "SITE WORK"), and
the initial leasehold improvements in the Premises (the "LEASEHOLD WORK") (the
Base Building Work, the Site Work and the Leasehold Work being collectively
referred to herein as "LANDLORD'S WORK") in substantial conformity with the Base
Building Plans, the Leasehold Work Plans and the Site Work Plans (such plans
being collectively referred to herein as the "PROJECT PLANS"). Schedule I
attached hereto, for clarity, conceptually outlines the Base Building Work.

         3.       Architect and Engineers.

                  (a) Landlord has employed Hellmuth, Obata & Kassabaum, P.C.
(the "BASE BUILDING Architect") to prepare plans for the Base Building Work (the
"BASE BUILDING PLANS"), such plans being identified on Schedule II). The Base
Building Architect has employed RG Vanderweil Engineers (the "BASE BUILDING
Engineers"), among others, to prepare engineering drawings relating to the Base
Building Work.

                  (b) Tenant shall employ Gensler (the "LEASEHOLD ARCHITECT") to
prepare all plans for the Leasehold Work (the "LEASEHOLD WORK PLANS"). Subject
to the following provisions of this Paragraph 3(b), Tenant shall employ RG
Vanderweil Engineers (in such capacity, the "LEASEHOLD ENGINEERS") to prepare
the engineering drawings relating to the Leasehold Work, subject to a written
scope of work and fee reasonably acceptable to Tenant being agreed to in
advance. If Tenant and such engineer are not able to agree to a scope of work
and the fee that is reasonably acceptable to Tenant, then Tenant shall have the
right to solicit competitive proposals from other qualified engineering firms
approved by Landlord, which approval shall not be unreasonably withheld,
conditioned or delayed. Landlord shall use


                                      B-1
<PAGE>   81

commercially reasonable efforts to direct its Base Building Architect and Base
Building Engineers to cooperate with Tenant's Leasehold Architect and Leasehold
Engineers (if such engineer is not RG Vanderweil Engineers) at no additional
cost to Landlord or Tenant for normal coordination and information gathering
activities between the architectural and engineering firms as reasonably
determined by Landlord. Tenant's Leasehold Architect and Leasehold Engineers (if
such engineer is not RG Vanderweil Engineers) will be required to submit all
requests for information of the Base Building Architect and Base Building
Engineers through Landlord and shall not contact or interact directly with the
Base Building Architect and Base Building Engineers without the prior written
consent of Landlord. Neither the Base Building Architect nor the Base Building
Engineers shall charge any costs or fees to Tenant directly or indirectly
through Landlord without Tenant's written approval of any such event or effort
that would give rise to such charges.

         4. Plans for Base Building Work. Landlord has heretofore prepared the
Base Building Plans. Landlord agrees that the design and construction of the
Base Building Work shall be in accordance with the final construction drawings
for the Base Building Work (subject to the modifications required by the
requirements of any applicable building code, insurance requirement or
government rule or regulation).

         5. Plans for Leasehold Work.

                  (a) Tenant shall cause the Leasehold Architect to prepare
programming and space plans for the Leasehold Work, in form approved by Tenant,
for submission to Landlord for its approval no later than June 30, 2000 (the
"SPACE PLAN"). If Landlord has any comments with respect to the programming and
space plans, Landlord shall make such comments known to Tenant within ten (10)
business days following submission of the programming and space plans to
Landlord.

                  (b) Tenant shall cause the Leasehold Architect to prepare
design development drawings for the Leasehold Work, in form approved by Tenant,
for submission to Landlord for its approval no later than August 18, 2000. If
Landlord has any comments with respect to the design development drawings,
Landlord shall make such comments known to Tenant within ten (10) business days
following submission of the design development drawings to Landlord.

                  (c) Tenant shall cause the Leasehold Architect and the
Leasehold Engineers to prepare final construction documents for the Leasehold
Work, in form approved by Tenant, for submission to Landlord for its approval no
later than October 6, 2000. If Landlord has any comments with respect to the
construction documents, Landlord shall make such comments known to Tenant within
ten (10) business days following submission of the construction documents to
Landlord. The construction documents for the Leasehold Work that have been
submitted by Tenant and approved by Landlord shall be referred to herein as the
"Leasehold Plans." Landlord shall specify in its approval of the Leasehold Plans
those improvements that Tenant must remove from the Premises upon the expiration
or earlier termination of the Lease. Tenant shall be solely responsible for the
compliance of the Leasehold Plans with all Legal Requirements and with all Loss
Control Guidelines established by Landlord's insurance carrier



                                      B-2
<PAGE>   82

and in effect as of May 1, 1999, which Loss Control Guidelines have been
provided by Landlord to Tenant.

                  (d) Notwithstanding anything herein to the contrary, all
plans, drawings and documents related to the Leasehold Work (and any change
orders related thereto) shall be submitted to Landlord for its approval in
accordance with this Exhibit, which approval shall not be unreasonably withheld,
conditioned or delayed with respect to nonstructural Alterations (as defined in
Article IX of the Lease), but which approval with respect to Structural
Alterations and with respect to any portion of such Leasehold Work that affects
the exterior of the Building or appearance from the main lobby of the Building
or other tenant premises in the Building, may be granted or withheld in
Landlord's sole and absolute discretion.

         6. Cost of Base Building Work and Site Work. Landlord shall bear all
costs of designing and constructing the Base Building Work. Landlord shall bear
all costs of designing the Site Work (the plans developed by Landlord with
respect thereto being referred to herein as the "SITE WORK PLANS") and of
constructing the Site Work in substantial conformity with the Site Work Plans.
Landlord shall bear all costs incurred in connection with proffers and
development conditions imposed by the applicable private and governmental bodies
and authorities, including but not limited to those arising from the approval of
the Base Building Plans, the Site Work Plans or the site plan for the
development of the Building.

         7. Cost of Leasehold Work. Immediately following approval of the
Leasehold Plans, Landlord shall solicit bids for performance of the Leasehold
Work from at least three (3) reputable, independent, qualified, licensed
contractors designated by Landlord and reasonably approved by Tenant (provided
that, if Tenant does not give Landlord written notice of its objection to a
proposed contractor within five (5) business days after the name of such
contractor is submitted to Tenant by Landlord, then Tenant shall be deemed to
have approved such contractor). Tenant shall have the right to designate, by
designating the same in writing to Landlord not later than August 11, 2000, one
(1) qualified, licensed contractor to be included among the contractors from
whom bids are solicited, subject to Landlord's reasonable approval of the
contractor thus designated by Tenant. Promptly after the bids are received,
Landlord shall provide Tenant with a summary (in Landlord's standard format) of
all the bids with complete copies of each bidder's response. Landlord shall
select the contractor, after consultation with Tenant, who will be employed to
perform the Leasehold Work from among the contractors submitting responsive bids
in response to Landlord's solicitation (the "LEASEHOLD CONTRACTOR"). The
criteria for selection of the Leasehold Contractor shall be the lowest qualified
price, ability to complete the work on time and expected performance value.
Landlord shall keep Tenant informed of the status of the bidding process and
shall follow all of its standard procedures in managing the build out of
comparable space. The cost of the design and construction of the Leasehold Work
(including all "soft" costs, and including Landlord's construction management
fee equal to three percent (3%) of the project costs, expressly excluding any
portion of the Leasehold Work that is performed or managed directly by Tenant
(collectively, the "LEASEHOLD COST")) up to the amount of the Improvements
Allowance described in Paragraph 8 below shall be borne by Landlord. Any portion
of the Leasehold Cost that is in excess of the Improvements Allowance shall be
borne by Tenant and is referred to herein as "TENANT'S EXPENSES." Tenant will be
billed by Landlord and shall pay Landlord for Tenant's Expenses on a pro rata
basis as



                                      B-3
<PAGE>   83

each requisition from the Leasehold Contractor is submitted for payment
by Landlord (so that the percentage of the Tenant's Expenses paid by Tenant at
the time of each requisition shall be equal to the percentage of the Leasehold
Work that has been completed by the Leasehold Contractor). All amounts payable
by Tenant pursuant to this Exhibit shall be considered additional rent and
subject to the provisions of the Lease. In consideration for the three percent
(3%) construction management fee, Landlord shall perform or cause the Leasehold
Contractor to perform preconstruction services, cost estimating, scheduling and
value engineering services, shall administer the bid process, shall identify
long-lead items and suggest alternative materials and substitutions, shall
negotiate and enter into contracts, shall negotiate, manage and administer
change orders, shall provide periodic progress reports on the Leasehold Work,
shall maintain construction records with respect to the Leasehold Work, shall
assemble operation manuals and shall cooperate with the Leasehold Architect in
preparing the "as-built" drawings for the Premises.

         8. Improvements Allowance.

                   (a) Landlord hereby agrees to grant Tenant an allowance (the
"IMPROVEMENTS ALLOWANCE") in an amount equal to the product of (i) Thirty
Dollars ($30.00) and (ii) the number of rentable square feet in the Premises, to
be applied toward the Leasehold Cost and the actual costs and expenses incurred
by Tenant in connection with moving into the Premises.

                  (b) In addition to the Improvements Allowance, provided no
Event of Default exists under the Lease, Landlord hereby grants to Tenant an
additional allowance (the "Additional Allowance") in the amount elected by
Tenant up to the product of Five Dollars ($5.00) multiplied by the number of
square feet of rentable area in the Premises. If Tenant desires to draw on the
Additional Allowance, Tenant must follow the written request procedure
applicable to draws of the Improvement Allowance. The Additional Allowance shall
only be applied toward Leasehold Costs and Tenant's Moving Costs, as defined
below, and other costs to which the Improvements Allowance may be applied. The
amount of the Additional Allowance must be drawn by Tenant no later than thirty
(30) days after the Lease Commencement Date and any portion of the Additional
Allowance that is not drawn by such date shall be deemed waived and forfeited by
Tenant. The amount of the Additional Allowance drawn by Tenant shall be treated
as an assumed loan, which shall be fully amortized over the initial one hundred
twenty (120) months of the Lease Term and shall be paid in equal monthly
installments together with interest on the outstanding balance of the Additional
Allowance at a fixed rate equal to ten percent (10%) per annum. Such additional
payment shall be added to and become part of the Base Rent payable in accordance
with the provisions of Article III of the Lease. Such amount shall be confirmed
in an amendment to the Lease.

                  (c) In the event the entire Improvement Allowance is not
utilized by Tenant in connection with designing, constructing and installing the
Leasehold Work, such unused portion of the Improvement Allowance shall be
applied, at Tenant's election, (i) against the first installment(s) of base rent
due with respect to the Premises pursuant to Article III of the Lease or (ii) an
amount not to exceed Five Dollars ($5.00) multiplied by the number of square
feet of rentable area in the Premises, may be applied (y) toward the purchase of
furniture and furnishings in the Premises or (z) actual cost and expenses
related to and incurred by Tenant in



                                      B-4
<PAGE>   84

connection with Tenant's normal, typical and reasonable expenses of moving into
the Premises, including packing and unpacking, telephone installation and moving
all of Tenant's furniture and equipment to relocate Tenant's offices ("Tenant's
Moving Costs"), or any combination thereof. Notwithstanding anything to the
contrary in this Paragraph 8(c), an amount not less than the product of
Twenty-Five Dollars ($25.00) multiplied by the Net Rentable Area of the Premises
of the Tenant Improvement Allowance shall be used by Tenant for the sole and
exclusive purpose of designing, construction and installing the Leasehold Work
including without limitation, preparation of drawings and specifications, the
installation of computer and telephone network equipment, cabling and wiring
which will remain in the Premises at the expiration of the Lease Term and such
other equipment which, under the terms of this Lease, will remain in the
Premises at the expiration of the Lease Term,

                  (d) Any portion of the Leasehold Cost that is in excess of the
sum of the Improvements Allowance plus the portion of the Additional Allowance
that Tenant elects to apply towards Leasehold Work is referred to herein as
"TENANT'S EXPENSES." On or before the twenty-fifth (25th) day of each month,
Landlord shall submit to Tenant's Authorized Representative and Leasehold
Architect a certified statement setting forth the portion of the Leasehold Cost
due and payable to Leasehold Contractor or otherwise on account of Leasehold
Work performed during the preceding calendar month, which statement shall
include, among other things, (i) a requisition in standard AIA format in the
same detail as that furnished to Landlord by the Leasehold Contractor for the
Leasehold Work, i.e., setting forth percentage of completion by trade, (ii) a
copy of the Leasehold Contractor's requisition with respect to the Leasehold
Work for such preceding calendar month, and (iii) a calculation of any amounts
then due to Landlord with respect to Tenant Expenses.

                 (e) Each time Tenant receives a statement from Landlord
described subparagraph (d) above, Tenant shall pay its proportionate share (if
any is due pursuant to the following sentence) of the amount billed for
Leasehold Work to Landlord or Landlord's Contractor (as directed by Landlord)
within ten (10) days after Tenant receives a request therefor from Landlord
(except to the extent the Leasehold Architect reasonably believes that there is
a bona fide dispute regarding the Leasehold Work, which disputed amount shall be
paid in accordance with the resolution of the dispute). Tenant's proportionate
share of each such monthly statement shall be determined by multiplying the
amount due the Leasehold Contractor for Leasehold Work (in accordance with this
Exhibit B) by a fraction, the numerator of which shall be the Tenant's Expenses
and the denominator of which shall be the Leasehold Cost. The portion of the
Leasehold Cost other than Tenant's said proportionate share shall be deducted by
Landlord from the Improvements Allowance and, if applicable, the Additional
Allowance, and paid to the Leasehold Contractor or other party. In the event of
an adjustment in the Leasehold Cost, such fraction shall be appropriately
adjusted so that at all times Tenant bears its proportionate share of the
Leasehold Cost computed in accordance with this paragraph.

               (f) All amounts payable by Tenant pursuant to this Exhibit B
(excluding amounts deducted from the Improvements Allowance and the Additional
Allowance) shall be considered additional rent and subject to the provisions of
Section 19.6 of the Lease. Tenant may begin drawing funds (up to an aggregate
amount of Five Dollars ($5) per square foot of rentable area) from either the
Improvements Allowance and/or the Additional Allowance following the date of



                                      B-5
<PAGE>   85

this Lease to pay for the costs theretofore or thereafter incurred by Tenant
with respect to the Leasehold Plans and other permitted purposes as set forth
above. Tenant shall furnish a written requisition for any portion of the
Improvements Allowance or the Additional Allowance that is to be applied toward
such expenses, which requisition shall be accompanied by appropriate invoices
from the Leasehold Architect, the Leasehold Engineers, or Tenant's project
manager, or other contractor as applicable and lien waivers with respect to all
work performed or services or materials provided through the date of each such
invoice (subject only to receipt of the requisitioned amount). Provided such
requisition, invoices and lien releases are received by Landlord no later than
the twenty-fifth (25th) day of a calendar month, Landlord shall use commercially
reasonable efforts to pay the amount of such requisition (up to the allowable
portion of the Improvements Allowance) by the twentieth (20th) day of the
immediately-succeeding calendar month. Tenant acknowledges that the Improvements
Allowance (or portions thereof) may be financed by a lender and Tenant agrees to
participate, if requested, in the draw process reasonably established by the
lender and to comply with the following requirements that may be imposed by
Landlord's lender as conditions to funding the Improvements Allowance:
submitting, if requested, copies of the Leasehold Plans to the lender and
responding to the lender's inquiries about the Leasehold Plans and obtaining
written lien releases and certifications from the Leasehold Architect that the
work covered by the requisition has been performed substantially in accordance
with the Leasehold Plans.

         9. Change Orders. If, after preparation and review of the Leasehold
Plans, Tenant requests any change or addition to the work and materials to be
provided pursuant to the Leasehold Plans, then such change order shall require
Landlord's approval. Tenant shall be responsible for any delay in completion of
Landlord's Work resulting from any change order requested by Tenant. In
addition, in the event a change order requested by Tenant with respect to the
Leasehold Plans causes the Leasehold Cost to exceed the amount of the
Improvements Allowance, then all additional expenses attributable to any such
change or addition requested by Tenant and approved by Landlord, including
Landlord's construction management fee equal to three percent (3%) of the net
increase in the cost of the Leasehold Work shall be payable by Tenant, within
ten (10) days after Landlord's submission of a statement of the additional
expenses attributable to such change order, as additional rent. The Leasehold
Architect (and after commencement of construction of the Leasehold Work only,
the Leasehold Contractor) shall be responsible to coordinate the Leasehold Plans
with field conditions. Landlord may make reasonable field substitutions (i.e.,
by substituting materials of comparable or better quality, cost and performance
specifications) for materials specified in the Leasehold Plans if any materials
specified in the Leasehold Plans cannot reasonably be obtained at the job site
in time to be incorporated into the Leasehold Work in the normal progression and
diligent prosecution of the Leasehold Work. No material substitutions shall be
made without Tenant's prior approval; however, if Tenant withholds or delays its
approval, any delay in obtaining and incorporating the originally specified
materials (and any consequent delay in completing other work that appropriately
must follow incorporation of such delayed materials into the Leasehold Work)
that is not necessitated by any default of the contractor shall be deemed a
Tenant Delay. As promptly as possible under the circumstances, after receiving a
request for a change or addition to the Leasehold Plans and Leasehold Work,
Landlord shall furnish Tenant with a proposal setting forth in reasonable detail
the Leasehold Contractor's good faith estimate of the additive or

                                      B-6
<PAGE>   86
deductive dollar amount of such change and the additive or deductive time
duration of such change.

         10. Substantial Completion.

                  (a) Except as provided in Paragraph 10(b) below, the Leasehold
Work shall be deemed to be substantially complete when (i) the Leasehold Work
(except for punch list items) has been substantially completed in substantial
conformity with the Leasehold Plans, and (ii) all conditions precedent to
issuance of a final non-residential use permit by the appropriate authorities of
Montgomery County, Maryland, with the exception of post-occupancy inspection by
the Fire Marshal, have been satisfied.

                  (b) Notwithstanding the foregoing, if Landlord shall be
delayed in completing the Leasehold Work as a result of: (i) Tenant's failure to
comply with any deadline specified in this Exhibit, (ii) Tenant's request for
changes to the Leasehold Plans subsequent to the date that such plans or working
drawings were prepared and reviewed, (iii) Tenant's failure to pay when due any
portion of the Tenant's Expenses or any other sums payable by Tenant pursuant to
this Exhibit, (iv) Tenant's request for materials, finishes or installations as
part of the Leasehold Work which constitute long-lead items, provided the same
are identified by Landlord promptly after Landlord's receipt of the bid
responses from the contractors who submitted bids for the performance of the
Leasehold Work, (v) any delay in obtaining a building permit with respect to the
Leasehold Work caused by the act or omission of Tenant, or (vi) the performance
(or failure thereof) of any work by any person or firm employed or retained by
Tenant (including, without limitation, the Leasehold Architect and the Leasehold
Engineers (with respect to the Leasehold Plans)), then for purposes of
determining the Lease Commencement Date, the work and materials to be provided
by Landlord pursuant to this Exhibit shall be deemed to have been substantially
completed on the date that they would have been substantially completed if such
delay or delays (each of which is referred to herein as a "TENANT DELAY") had
not occurred. Landlord shall endeavor to notify Tenant promptly if Landlord
becomes aware of the existence of any such delay. Landlord agrees to use good
faith reasonable efforts to counter the effect of any Tenant Delay; however,
Landlord shall not be obligated to expend any additional amounts in such efforts
(e.g., by employing overtime labor) unless Tenant agrees in advance to bear any
incremental cost associated with such efforts (whether or not such efforts are
ultimately successful). Notwithstanding the foregoing, a Tenant Delay shall not
be deemed to have delayed Substantial Completion unless there is a direct
causation between the Tenant Delay and Landlord's failure to achieve Substantial
Completion. By way of example, if (I) the Lease Commencement Date is delayed by
twenty (20) days, (II) there had been no delays the Lease Commencement Date
would have occurred on or before April 15, 2001 and (III) fifteen (15) days of
the delay are Landlord delay and five (5) days of the delay are Tenant Delay,
then the Lease Commencement Date would be April 30, 2001.

                  (c) With respect to long-lead items, Tenant shall have ten
(10) days following receipt of the bid summary and related bid response
information from Landlord to elect (i) to omit such long-lead item(s) from the
Leasehold Plans, (ii) substitute such item(s) for another item(s) that does not
constitute a long-lead item or (iii) retain such long-lead item (s) in the
Leasehold Plans to be installed when delivered. In the event Tenant fails timely
to affirmatively



                                      B-7
<PAGE>   87

elect (i), (ii) or (iii) above, Tenant shall be deemed to have elected (iii).
Landlord shall promptly identify for Tenant after the time of submittal by
Tenant of a proposed substitution, the estimated delay which will be caused by
such substitution, if any. In no event shall the Lease Commencement Date be
extended due to a delay in the completion and installation of the long-lead item
or arising from Tenant's election to omit, substitute or retain an identified
long-lead item that Tenant has been notified of in accordance with the
provisions of this Work Agreement.

         11. Punchlist and Possession. Prior to the Lease Commencement Date,
Landlord shall schedule a mutually agreeable time with Tenant to walk through
the Premises and prepare a punchlist setting forth any defects or incomplete
work. Tenant's taking of possession of the Premises shall constitute Tenant's
acknowledgement that the Premises are in good condition and that all work and
materials are satisfactory, except as to any items set forth in such punchlist
and except as to latent defects discovered by Tenant within one (1) year
following the Lease Commencement Date. Landlord will endeavor promptly to
correct and complete those defects and incomplete items described in such
punchlist within thirty (30) days, and will promptly correct any latent defects
timely brought to Landlord's attention by Tenant.

         12. [Intentionally Deleted]


/s/ RAR
----------------------------
Landlord's initials

/s/ RAK
------------------------
Tenant's initials



                                      B-8
<PAGE>   88


                                   SCHEDULE I
                                       To
                                    EXHIBIT B
                                   SHELL ITEMS

     o   Building structure including foundations, slab on grade, supported
         slabs, structural concrete and post tensioned concrete slabs and beams.

     o   Fireproofing of structural steel as required by code.

     o   Men's and women's toilet rooms substantially complete including
         plumbing and fixtures, paint and lighting per code (on the Lease
         Commencement Date such facilities shall be fully operational in a first
         class manner in accordance with the requirements of the Lease).

     o   Drinking fountains installed per code (i.e. not less than two (2) water
         coolers and wet stacks per floor).

     o   Electrical closets complete with tenant panel for power and lighting.

     o   Building fire stairs complete.

     o   Mechanical equipment rooms complete with air handlers and ductwork.

     o   Mechanical penthouse substantially complete with base building
         equipment.

     o   Elevators, cabs, frames and entries.

     o   Primary HVAC loop ductwork from the mechanical rooms around the cores.

     o   VAV boxes at a ratio of one box with control thermostat per 1200 RSF
         (coiled up awaiting tenant walls).

     o   Drywall ready for paint around columns, outside of cores and perimeter
         wall.

     o   Fire command center substantially complete.

     o   Fire alarm system with connections to base building equipment (tamper
         and flow switches, HVAC units, elevators, etc.). System to be sized to
         accept tenant devices (for standard office usage).

     o   Fire sprinkler pump (if required) with tamper and flow switches on the
         risers, sprinkler loop on each floor with heads in base building areas
         (toilet, mechanical, stair towers, penthouse, etc.).

     o   Electrical capacity in the bus duct will be provided at 2 watts/RSF
         "connected" for lighting and 6.5 watts/RSF "connected" for power.

     o   Perimeter security system.

     o   Loading dock with exterior doors and bumpers.

     o   Exit lights at each base building exit.

     o   Base building emergency generator (for Base Building/life safety use
         only).

     o   One inch aluminum window blinds.



                                      B-9
<PAGE>   89










                                   SCHEDULE II
                                       To
                                    EXHIBIT B
                    LIST OF BUILDING PLANS AND SPECIFICATIONS
                                [To Be Attached]









                                      B-10
<PAGE>   90


                                  SCHEDULE III
                                       To
                                    EXHIBIT B
                      RULES AND PROCEDURES FOR CONTRACTORS

         The following requirements have been developed to ensure that
modifications or improvements to the building and/or building systems and
equipment are completed to building standards while maintaining a level of
safety consistent with industry standards. The review of tenant plans and/or
specifications by Landlord, Boston Properties, Inc. and/or their insurers,
consultants or other representatives, does not imply that any plans so reviewed
comply with applicable laws, ordinances, codes, standards or regulations.

         I. GENERAL

         A. No work will be performed until the Landlord's Representative has
received two (2) sets of drawings and specifications, the plans and given
approval.

         B. All modifications to the building or to the building systems and
equipment must be compliant with local codes and/or ordinances.

         C. Impairments to fire/life safety systems and hot work conducted
during the project will be conducted in accordance with the requirements of the
Landlord's insurance loss control programs.

         D. Prior to the work commencing, a building permit must be obtained and
displayed and a certificate of insurance from the contractor must be furnished
to Boston Properties naming the following entities as an additional insured: (i)
Boston Properties Limited Partnership, a Delaware limited partnership; (ii)
Boston Properties, Inc., a Delaware corporation; (iii) BP Management, LP, a
Delaware limited partnership, (iv) Boston Properties, LLC, a Delaware limited
liability company and Wells Fargo Bank, National Association.

         E. At the completion of the work, the contractor shall furnish the
owner with one set of reproducible and two (2) sets of blue-line prints showing
the final as-built construction work performed.

         F. The Landlord's Representative will be notified by the contractor of
all work scheduled and will be provided a list of all personnel working in the
building.

         G. No work will be performed from 8:00 a.m. to 6:00 p.m. which will
disturb or inconvenience tenants in the building (e.g. core drilling, shooting
track, noxious odors, etc.). The Landlord's Representative must preapprove any
work that entails significant noise of vibration.

         H. Before any new electrical or mechanical equipment is installed in
the building, the contractor will submit a copy of the manufacturer's data sheet
to the Landlord's Representative.



                                      B-11
<PAGE>   91

         I. All carts must be furnished with pneumatic tires.

         J. Smoking is not allowed in any occupied building.

         K. The use of radios is prohibited.

         L. This is a post tensioned concrete structure, all slabs must be
x-rayed and x-rays reviewed by the building's structural engineer prior to core
drilling. If obstructions are detected, consult with the Landlord's
Representative or relocate the core drill as necessary.

         M. The contractor must furnish the Landlord's Representative with a
list of all subcontractors including emergency phone and/or pager numbers prior
to commencing the work.

         N. The contractor must provide an on-site project superintendent at all
times during which construction work is in progress. This supervisor must be
knowledgeable of the project's scope of work and have adequate on-site reference
materials such as plans and specifications.

         O. All workers must be dressed appropriately when working in an
occupied building. Shirts must be worn at all times.

         P. Prior to start of work, all blinds must be raised and bagged and
windowsills protected. Workers must not stand on windowsills or other building
components.

         Q. Any work that requires access to another tenant's space must first
be coordinated through the Landlord's Representative. All cost associated with
security or building engineering services shall be charged to the contractor.

         R. Any roof related work must be performed by Landlord's designated
contractor.

         S. Dumping of construction debris into building drains, mop sinks, etc.
is strictly prohibited

         II. LIFE SAFETY

         A. Contractor will not disconnect, tamper with, delete, obstruct,
relocate, or expand any life safety equipment except as indicated on approved
drawings.

         B. Contractor will take necessary precautions to prevent accidental
fire alarms. Any unit or device temporarily incapacitated will be red-tagged
"Out of Service" and the Landlord's Representative will be alerted prior to the
temporary outage. See attached "Guidelines for Managing Construction Project
Fire Protection Impairment".

         C. All tenant installed special fire extinguisher/alarm detection
systems shall be monitored by the base building fire alarm system.



                                      B-12
<PAGE>   92

         D. Tenant installed fire alarm initiation and notification devices
operating directly from the base building fire alarm system shall be specified
by the Landlord.

         E. All connections to the building's existing fire alarm system are to
be made only by the subcontractor specified by the Landlord's Representative.

         F. All fire alarm testing will be scheduled at least 72 hours in
advance with the Landlord's Representative and must be scheduled to occur after
normal business hours.

         G. Combustible and hazardous materials are not allowed to be stored in
the building without prior approval of the Landlord's Representative. Material
safety data sheets on all other materials to be stored in the building must be
kept on site and a copy submitted to the Landlord's Representative.

         H. Dust protection of smoke detectors must be installed and removed on
a daily basis. Dust protection is required during construction to avoid false
fire alarms. Filter media must be installed over all return air paths to any
equipment rooms prior to demolition. The media must be maintained during
construction and removed at substantial completion.

         I. All buildings are to be fully protected by automatic sprinkler
systems.

         J. All systems and equipment are to be designed and installed in
accordance with the current standards of the National Fire Protection
Association.

         K. All equipment, devices and materials used in the installation should
be listed by UL and FM Approved.

         L. Connections to the base building sprinkler system/standpipe riser
shall be provided with a control valve and water flow alarm device. Sprinkler
systems control valves shall be UL Listed and FM Approved, clockwise closing,
indicating valves with supervisory switches.

         M. The entire system should be designed and installed in accordance
with NFPA Pamphlet No. 13, 231 and 231C latest issues.

Note #1: If concealed type sprinkler heads are to be utilized in office areas,
the system is to be designed as an Ordinary Hazard Group 1 System.

Note #2: For light hazard designed systems, the hydraulically most remote design
area shall not be allowed a 40% reduction. The minimum design area shall be 1500
square feet.

         N. Enclosed, as Attachment "A", is a copy of the Guidelines for
Managing Construction Project Fire Protection Impairments with Impairment Log
and Tenant Build Out Project Requirements. Coordinate Impairment Log with the
Landlord's Representative.



                                      B-13
<PAGE>   93

         III. PARKING - LOADING DOCK

         A. Contractors or their personnel will not use loading dock area for
daytime parking without first obtaining permission from the Landlord's
Representative 48 hours in advance to better assure dock availability.
Unauthorized vehicles will be ticketed and towed.

         B. Use of the loading dock for deliveries/trash removal must be
scheduled through the Landlord's Representative.

         C. Material that does not fit into the protected elevator must be
delivered through a window opening. The contractor will be responsible to remove
and replace the glass and to adequately protect the window framing with prior
approval from the Landlord's Representative.

         D. Removal and replacement of exterior glass must be performed by
Landlord's designated contractors.

         IV. UTILITIES

         A. Utilities (i.e. electric, gas, water, telephone/cable) will not be
cut off or interrupted without permission of the Landlord's Representative and
affected tenants and at least 48 hours prior notice.

         V. SECURITY

         A. When it is deemed necessary by the Landlord's Representative to
temporarily issue any keys to a contractor, said contractor will be responsible
for controlling possession and use of the key(s) and will return them daily to
the person that issued them.

         B. The contractor will be responsible for locking any area made
available to him/her whenever that area is unattended.

         C. Contractors may be required to wear Boston Properties identification
badges. The badges will be issued by the Landlord's Representative if required.

         VI. ELEVATORS

         A. No passenger elevators will be used to move construction material or
construction personnel.

         B. The service elevator can be used to move construction personnel at
any time during the day as long as the elevator doors do not have to be held
open. The service elevator can not be used to move construction materials into
the building between the hours of 7:30 am and 5:00 pm. After these hours, all
usage must be scheduled with the Landlord's Representative with at least 48
hours notice.



                                      B-14
<PAGE>   94

         C. Any costs to repair damage to the elevators including dust or dirt
in machine rooms or shaft or costs for service calls resulting from the
contractor's operations will be charged to the contractor.

         VII. CLEANING

         A. Contractors will remove their trash and debris daily or as often as
necessary to maintain cleanliness in the building(s). The building trash
compactors or containers are not to be used for construction debris.

         B. Walk-off mats should be provided at door entrances where work is
being performed.

         C. Carpeting shall be protected by plastic runners or hardboard as
necessary to maintain cleanliness and to protect carpets from damage.

         D. Contractor will furnish a vacuum(s) with a supply of clean bags to
facilitate ongoing clean- up.

         E. Trash removal will be scheduled and coordinated with the Landlord's
Representative.

         F. Contractors must remove all food cartons from the work area on a
daily basis.

         VIII. MECHANICAL AND ELECTRICAL WORK

         A. The installation or modification to building HVAC systems must be
submitted for review by the building owner. This would include base building
systems as well as supplemental units and/or exhaust or system.

         B. The mechanical plan must show size and location of all supply and
return grilles.

         C. Contractors modifying duct work, air grilles, VAV boxes, etc...,
shall be responsible for balancing the air and water supplies as necessary and
all air balancing is to be done in the presence of a Landlord's Representative.

         D. Any domestic or condenser water connections made to the building's
piping system, must include a high quality isolation valve, (brass bodied gate
or ball-type) and adequate system drain valves. If the system piping is of a
different material a dielectric union must be installed. All valves must be
easily accessible.

         E. Exhaust fans will not be installed which discharge into a return
ceiling plenum. Such fans will be ducted to the outside via exhaust shafts or
other routes as approved by the Landlord's Representative.



                                      B-15
<PAGE>   95

         F. Where independent tenant-owned air conditioning units are installed,
a submeter will be used or a flat rate charge negotiated with tenant based on
anticipated consumption.

         G. All wiring that is not reusable for telecommunications and
electrical systems including conduit, BX cable, electric or telephone wiring
shall be removed from the ceiling back to the originating terminal block or
panel.

         H. The installation of tenant equipment (except lighting per code) on
the base building emergency power supply systems is not permitted.

         I. Any existing mechanical systems and their controls that are to
remain shall be properly "commissioned". That is, at the beginning of the job
the systems will be turned over to the contractor in working condition by the
Landlord's Representative. Before beginning any work, the contractor should
inspect the mechanical systems and their controls to ensure their working
condition. The contractor should advise the Landlord's Representative of any
noted deficiencies. At the end of the job, the contractor will be responsible
for the proper operation of the mechanical systems. If the contractor fails to
note any deficiencies at the outset of the job, the contractor will,
nevertheless be required to correct the problems before the system is accepted
by the Landlord's Representative.

         J. All circuit breaker panels must be clearly and accurately labeled
with typed labels.

         K. All smoke detectors shall be properly protected with bags prior to
start of work. Bags shall be removed upon completion.

         L. All base building mechanical equipment shall be properly protected
with prefilters, dust covers etc. prior to start of work. Protection shall be
removed and equipment wiped down at completion.

         M. Landlord's designated contractor must perform final fire alarm
connections.

         N. Tenant shall obtain from Landlord the Tenant Design Guidelines for
mechanical and electrical requirements for the building. Note all new mechanical
systems, VAV boxes, diffusers and controls shall match existing base building.



                                      B-16
<PAGE>   96

                                   SCHEDULE IV
                                       To
                                    EXHIBIT B

                 INSURANCE REQUIREMENTS FOR TENANT'S CONTRACTOR

Tenant's Contractors shall procure and maintain for the duration of the contract
insurance against claims for injuries to persons or damages to property which
may arise from or in connection with the performance of the work hereunder by
the contractor, his agents, representatives, employees, or subcontractors. The
cost of such insurance shall be included in the contractor's bid, unless
otherwise specified.

A. Minimum Scope of Insurance. Coverage shall be at least as broad as:

         1. Insurance Services Office "occurrence" form CG 00 01 (ed. 10/93)
         covering commercial general liability or its equivalent

         2. Insurance Services Office form CA 00 01 (ed. 6/92) covering
         automobile liability, Code 1 "Any Auto" and Endorsements CA 22 32 ed.
         4/92) and CA 01 12 (ed. 6/91)

         3. Workers compensation insurance as required by labor code of the
         State and employers liability insurance.

B. Minimum Limits of Insurance. Contractor shall maintain limits no less than:

         1. Commercial general liability: $1,000,000 combined single limit per
         occurrence for bodily injury and property damage. Minimum $2,000,000
         aggregate. (The general aggregate limit shall apply separately to this
         project/location or the general aggregate shall be twice the required
         limit.)

         2. Automobile liability: $1,000,000 combined single limit per accident
         for bodily injury and property damage.

         3. Workers compensation and employers liability: Workers compensation
         limits as required by the labor code of the State and employers
         liability limits of $1,000,000 per accident.

         4. Umbrella Liability: $5,000,000 per occurrence and $5,000,000
         aggregate (The aggregate limit shall apply separately to this
         project/location).

C. General liability and automobile liability coverage

         1. The tenant and Boston Properties and their respective officers,
         officials, and employees are to be covered as additional insureds as
         respects: liability arising out of activities performed by or on behalf
         of the contractor; products and completed



                                      B-17
<PAGE>   97

         operations of the contractor; premises owned, leased, or used by the
         contractor; or automobiles owned, leased, hired, or borrowed by the
         contractor. The coverage shall contain no special limitations on the
         scope of protection afforded.

         2. The contractor's insurance coverage shall be primary insurance as
         respects the city, its officers, officials, and employees. Any other
         insurance or self-insurance maintained by the agency, its officers,
         officials, and employees shall be excess of and not contribute with the
         contractor's insurance.

         3. Any failure to comply with reporting provisions of the policies
         shall not affect coverage provided to the agency, its officers,
         officials, and employees.

         4. The contractor's insurance shall apply separately to each insured
         against whom claim is made or suit is brought except with respect to
         the limits of the insurer's liability.

D. Workers compensation and employers liability coverage. The insurer shall
agree to waive all rights of subrogation against the agency, its officers,
officials, and employees for losses arising from work performed by the
contractor for the agency.

E. All coverage. Each insurance policy required by this clause shall be endorsed
to state that coverage shall not be suspended, voided, canceled by either party,
reduced in coverage or in limits except after 30 days' prior written notice by
certified mail, return receipt requested, has been given to the city.

F. Acceptability of Insurers. Insurance is to be placed with insurers licensed
to do business in the State with a Best's rating of no less than A- unless
specific approval has been granted by the Mayor's Office of Operations.

G. Verification of Coverage. Contractor shall furnish the city with certificates
of insurance effecting coverage required by the clause. The certificates for
each insurance policy are to be signed by a person authorized by that insurer to
bind coverage on its behalf. The certificates are to be on forms that are to be
received and approved by the agency before work commences. In addition, the
agency shall require an endorsement naming the city, its officers, and employees
as an additional insured. The agency reserves the right to obtain complete,
certified copies of all required insurance policies, at any time.

H. Subcontractors. Contractors shall include all subcontractors as insureds
under its policies or shall furnish separate certificates for each
subcontractor. All coverage for subcontractors shall be subject to all of the
requirements stated herein. Commercial general liability coverage shall include
independent contractors coverage, and the contractor shall be responsible for
assuring that all subcontractors are properly insured.



                                      B-18
<PAGE>   98

                                    EXHIBIT C
                              RULES AND REGULATIONS

         This Exhibit C is attached to and made a part of that Lease Agreement
dated as of June 27, 2000 (the "LEASE"), between BOSTON PROPERTIES LIMITED
PARTNERSHIP ("LANDLORD") and OTG SOFTWARE, INC. ("TENANT"). Unless the context
otherwise requires, the terms used in this Exhibit C that are defined in the
Lease shall have the same meanings as provided in the Lease.

         The following rules and regulations have been formulated for the safety
and well-being of all tenants of the Building and to insure compliance with
municipal and other requirements. Strict adherence to these rules and
regulations is necessary to guarantee that each and every tenant will enjoy a
safe and undisturbed occupancy of its premises in the Building. Any continuing
violation of these rules and regulations by Tenant shall constitute a default by
Tenant under the Lease.

         The Landlord may, upon request of any tenant, waive the compliance by
such tenant of any of the following rules and regulations, provided that (i) no
waiver shall be effective unless signed by Landlord, or its authorized agent,
(ii) any such waiver shall not relieve such tenant from the obligation of
complying with such rule or regulation in the future unless otherwise agreed to
by Landlord, (iii) no waiver granted to any tenant shall relieve any other
tenant from the obligation of complying with these rules and regulations, unless
such other tenant has received a similar written waiver from Landlord, and (iv)
any such waiver by Landlord shall not relieve Tenant from any liability to
Landlord for any loss or damage occasioned as a result of Tenant's failure to
comply with any rule or regulation.

         1. The sidewalks, entrances, passages, courts, elevators, vestibules,
stairways, corridors, halls, and other parts of the Building not exclusively
occupied by any tenant shall not be obstructed or encumbered by any tenant or
used for any purpose other than ingress and egress to and from each tenant's
premises. If a tenant's premises are situated on the ground floor of the
Building, the tenant thereof shall, at such tenant's own expense, keep the
sidewalks and curb directly in front of its premises clean and free from ice and
snow. Landlord shall have the right to control and operate the public portions
of the Building, and the facilities furnished for common use of the tenants, in
such manner as Landlord deems best for the benefit of the tenants generally. No
tenant shall permit the visit to its premises of persons in such numbers or
under such conditions as to interfere with the use and enjoyment of the
entrances, corridors, elevators and other public portions or facilities of the
Building by other tenants.

         2. No awnings, projections, pictures or other items shall be attached
to the outside walls of the Building without the prior written consent of
Landlord. No drapes, blinds, shades, screens, pictures, paper or other items
shall be attached to or hung in, or used in connection with, any window or door
of the Premises, without the prior written consent of Landlord. All awnings,
projections, curtains, blinds, shades, screens, lighting, ceiling tiles, wall
surfaces and other fixtures, including those used within the interior of the
Premises if visible from outside the Premises, must be of a quality, type,
design and color, and attached in the manner approved by Landlord. No furniture,
configurations, material and equipment storage (including the temporary



                                      C-1
<PAGE>   99

stacking of boxes) or interior decorations in the Premises that are visible from
outside the Premises shall be placed in the Premises without the prior written
consent of Landlord.

         3. No showcases or other articles shall be put in front of or affixed
to any part of the exterior of the Building, nor placed in the halls, corridors
or vestibules without the prior written consent of Landlord.

         4. The water and wash closets and other plumbing fixtures shall not be
used for any purposes other than those for which they were constructed, and no
debris, rubbish, rags, or other substances shall be thrown therein. All damage
resulting from any misuse of the fixtures shall be borne by the tenant who, or
whose servants, employees, agents, visitors or licensees, shall have caused the
same.

         5. There shall be no marking, painting, drilling into or defacement of
the Building or any part of the Premises that is visible from public areas of
the Building. Tenants shall not construct, maintain, use or operate within their
respective premises any electrical device, wiring or apparatus in connection
with a loud speaker system or other sound system, except as reasonably required
as part of a communication system approved prior to the installation thereof by
Landlord. No such loud speaker or sound system shall be constructed, maintained,
used or operated outside of the Premises.

         6. No bicycles or vehicles and no animals, birds or pets of any kind
shall be brought into or kept in or about the Building or any tenant's premises,
except that this rule shall not prohibit the parking of bicycles or vehicles in
the parking deck or the surface parking areas appurtenant to the Building. No
cooking or heating of food shall be done or permitted by any tenant on its
premises. No tenant shall cause or permit any unusual or objectionable odors to
be produced upon or permeate from its premises.

         7. No space in the Building shall be used for the manufacture of goods
for sale in the ordinary course of business, or for the sale at auction of
merchandise, goods or property of any kind. Furthermore, the use of its premises
by any tenant shall not be changed without the prior approval of Landlord.

         8. No tenant shall make any unseemly or disturbing noises or disturb or
interfere with occupants of this or neighboring buildings or premises or those
having business with them, whether by the use of any musical instrument, radio,
talking machine, whistling, singing, or in any other way. No tenant shall throw
anything out of the doors or windows or down the corridors or stairs of the
Building.

         9. No flammable, combustible or explosive fluid, chemical or substance
shall be brought into or kept upon the premises.

         10. No additional locks or bolts of any kind shall be placed upon any
of the doors or windows by any tenant, nor shall any changes be made in any
existing locks or the locking mechanism therein, without Landlord's approval.
The doors leading to the corridors or main halls shall be kept closed during
business hours except as they may be used for ingress or egress.



                                      C-2
<PAGE>   100

Each tenant shall, upon the termination of its tenancy, restore to the Landlord
all keys of stores, offices, storage and toilet rooms either furnished to, or
otherwise procured by, such tenant, and in the event of the loss of any keys so
furnished, such tenant shall pay to Landlord the replacement cost thereof.
Tenant's key system shall be separate from the rest of the Building.

         11. Landlord reserves the right to inspect all freight to be brought
into the Building and to exclude from the Building all freight which violates
any of these rules and regulations or the Lease.

         12. No tenant shall pay any employees on its premises, except those
actually working for such tenant at the tenant's premises.

         13. Landlord reserves the right to exclude from the Building at all
times any person who is not known or does not properly identify himself to the
Building management or watchman on duty. Landlord may, at its option, require
all persons admitted to or leaving the Building between the hours of 7:00 p.m.
and 7:30 a.m., Monday through Friday, and at any hour on Saturdays, Sundays, and
legal holidays, to register. Each tenant shall be responsible for all persons
for whom it authorizes entry into the Building, and shall be liable to Landlord
for all acts or omissions of such persons.

         14. The Premises shall not, at any time, be used for lodging or
sleeping or for any immoral or illegal purpose.

         15. Each tenant, before closing and leaving its premises any time shall
see that all windows are closed and all lights turned off.

         16. Landlord's employees shall not perform any work or do anything
outside of their regular duties, unless under special instruction from the
management of the Building. The requirements of tenants will be attended to only
upon application to Landlord, and any such special requirements shall be billed
to Tenant (and paid when the next installment of rent is due) in accordance with
the schedule of charges maintained by Landlord from time to time or at such time
as is agreed upon in advance by Landlord and Tenant.

         17. Canvassing, soliciting and peddling in the Building is prohibited
and each tenant shall cooperate to prevent the same.

         18. There shall not be used in any space or in the public halls of the
Building, either by any tenant or by jobbers or others in the delivery or
receipt of merchandise, any hand trucks except those equipped with rubber tires
and side guards. Tenant shall be responsible to Landlord for any loss or damage
resulting from any deliveries made by or for Tenant to the Building.

         19. Mats, trash or other objects shall not be placed in the public
corridors of the Building.

         20. Landlord does not maintain suite finishes which are non-standard,
such as kitchens, bathrooms, wallpaper, special lights, etc. However, should the
need arise for repairs of



                                      C-3
<PAGE>   101

items not maintained by Landlord, Landlord will arrange for the work to be done
at Tenant's expense.

         21. Drapes installed by Landlord for the use of Tenant or drapes
installed by Tenant, which are visible from the exterior of the Building, must
be cleaned by Tenant at least once a year, without notice, at Tenant's own
expense.

Initials of:

/s/ RAR
----------------------
Landlord

/s/ RAK
---------------------
Tenant




                                      C-4
<PAGE>   102

                                    EXHIBIT D
                    FORM OF DECLARATION OF LEASE COMMENCEMENT

This Exhibit D is attached and made a part of that certain Office Lease dated
_________, 200_ (the "LEASE"), between BOSTON PROPERTIES LIMITED PARTNERSHIP
("LANDLORD") and OTG SOFTWARE, INC. ("TENANT"). The terms used in this Exhibit D
that are defined in the Lease shall have the same meanings as provided in the
Lease. The Declaration to be executed by Landlord and Tenant pursuant to Section
2.3 of the Lease shall provide as follows:

"This Declaration made as of the ____ day of ____________, 200_ is being
provided pursuant to the terms and provisions of that certain Office Lease dated
____________, 200_, (the "Lease"), between Boston Properties Limited Partnership
("LANDLORD") and OTG Software, Inc. ("TENANT"). The parties to the Lease desire
to confirm that the following terms which are defined in the Lease shall have
the same meanings set forth below for all purposes in the Lease:

1.   The Lease Commencement Date is ____________, 200__.

2.   The initial term of the Lease shall expire on ____________, 200_.

3.   The number of square feet of rentable area in the Premises is ____________.

4.   The annual base rent with respect to the Premises for the first Lease Year
     is an amount equal to the product of ____________ Dollars ($________)
     multiplied by the total number of square feet of rentable area in the
     Premises.

5.   For the purposes of Article IV hereof, Tenant's Proportionate Share is
     __________ (_____%).

6.   As of the date hereof the Lease has not been modified and is in full force
     and effect and there are no defaults thereunder.

     Attached to this Declaration is evidence of payment of all insurance
required pursuant to Article XIII of the Lease."

Initials of:

---------------
Landlord

--------------
Tenant



                                      D-1
<PAGE>   103

                                    EXHIBIT E
                            JANITORIAL SPECIFICATIONS

         The contractor, furnishing all labor and material, agrees to conform to
the following minimum specifications with the understanding that to achieve an
acceptable standard of cleaning, frequencies will be increased as necessary.

Carpeting: All carpeted common areas including elevators and walk-off mats will
be cleaned every three (3) months by the extraction method or a combination of
shampooing and extraction if required.

Trash: Although trash is to be collected in a standard manner from each
individual office and trash receptacle, and deposited at a central location, our
recycle program requires that our individual tenants deposit recyclable trash at
a common location in each tenant suite. It will be the janitorial contractor's
responsibility to remove the recyclable trash from this common location and
place the trash in separate recycle containers on the loading dock. Since some
tenants may request that the janitorial contractor pick up the recyclable trash
within the individual offices, you should submit an alternate cost per work
station that can be charged to tenants requiring this additional service.

Paper Supplies: Paper products will be Scott 151 or owner approved equivalent.
Contractor will also furnish all feminine hygiene supplies and will collect
monies for same. These feminine hygiene supplies will not be charged back to the
owner.

Repairs/Logbook: Employees of contractor shall report daily, in writing, to
Boston Properties' office, any conditions such as leaky faucets, broken fixtures
and toilet seats, stopped-up drains, broken glass, any ceiling or exit lights
that need replacing and/or any other physical defect or unusual happening they
may encounter. These items are to be recorded in a log book provided by the
Property Manager. The last item noted in the log book will be a staffing
attendance summary indicating the number of persons who worked in the building
by job type and hour.

Lights: All lights should be switched off upon completion of cleaning in any
given area.

Uniforms: All contractor personnel will wear some form of neat and clean
consistent uniform and visible photo identification badge.

Staffing: Contractor will provide a staffing plan and designate all work
functions. If supervisors also have production responsibilities, the hours for
each task will be noted. At least one supervisor on each shift must be fluent in
spoken and written English and carry a pager.

Proposals will include an hourly credit to be applied on a quarterly basis for
all hours planned in the contractors proposal that were not actually expanded in
the building.

Equipment: Contractor will provide a list of all equipment to be maintained on
site. All new equipment will be provided at start up. Equipment will include at
least one operable wet vacuum.



                                      E-1
<PAGE>   104

All vacuum cleaners, trash barrels, and carts must be equipped with edge guards
to protect walls, furniture and baseboards.

Partial Occupancy: Proposals will include vacancy credits specified by minimum
floor areas.

Periodic Schedule: An up-to-date schedule of all periodic work will be posted on
site. Periodic work is considered to be all functions performed monthly or less
frequently. The schedule will chart 18 months and updated daily as scheduled
work is completed.

Day Schedule: A specific schedule for all day staff will be posted on site. At
least one person on the day staff must be a trained supervisor. This schedule
includes early morning clean up of building exterior.

Frequencies: Monday through Friday, except holidays as noted. Proposals should
specify the amount that would be charged if normal janitorial service is
requested for any of the designated holidays.

1.   Daily

     (a) Empty and wipe wastebaskets and ash trays. Sanitize as necessary.
Replace trash can liners nightly.

     (b) Clean cigarette urns.

     (c) Sweep entire floor area, including all lobbies, emergency exists, and
stairways. Damp mop or otherwise clean any floor area soiled due to spillage or
other cause.

     (d) Maintain lobbies to high standards at all times. Glass doors to be
cleaned and all metal polished as required.

     (e) Vacuum all carpeted areas including stairwells.

     (f) Buff shine all hard surface floors.

     (g) Elevators to be thoroughly cleaned and wiped including tracks. Only one
elevator may be taken out of service at any one time.

     (h) Police sidewalks, driveways, loading docks and grounds around building.

     (i) Spot wash to remove smudges and marks from walls, doors, glass, and
partitions as required.

     (j) Clean and polish all drinking fountains.

     (k) Carpet spotting throughout building to be done as necessary.

     (l) Dust all desk tops, table tops and incidental furniture.

     (m) Brush all fabric covered chairs with a lint brush.

     (n) Damp wipe all telephones including dials and crevices.

     (o) Clean and disinfect all toilet rooms and fixtures, and clean mirrors.
Pour one once of bowl cleaner into urinals and toilet bowls after cleaning and
do not flush.

     (p) Refill paper towel, toilet paper and soap dispensing units. Empty and
clean paper towel and sanitary napkin disposal receptacles.

2.   Weekly

     (a) Wipe clean all interior and exterior duronotic.



                                      E-2
<PAGE>   105

     (b) Completely dust office with cloth, including tops of files, ledges,
window sills, baseboards, chair rails, door louvers and trim.

     (c) Damp wipe all desk tops, table tops and incidental furniture.

3.   Monthly

     (a) Damp mop and buff all hard surface floors including telephone and
electrical closets. Strip, wax and polish floor areas receiving considerable
traffic, such as aisles, coffee rooms, cafeterias, and reception areas.

     (b) Machine scrub toilet room floors and completely disinfect all room
surfaces. Clean floor drains and pour in 2 cups of water and disinfectant
solution.

     (c) Dust all pictures, frames, charts, registered, molding, ledges, grills,
exteriors of lighting fixtures, etc.

     (d) Wash all stairwell landings and treads.

     (e) Wash all interior glass walls and glass partitions.

4.   Quarterly

     (a) Wash all wastebaskets.

     (b) Strip and refinish all hard surfaces floors not covered monthly.

     (c) Wipe down all walls.

     (d) Dust venetian blinds and window frames.

     (f) Thoroughly clean all elevator light fixtures and ledges.

     (g) Vacuum and dust all books in place.

     (h) Vacuum all upholstered furniture including each cushion.

5.   Semiannually

     (a) Vacuum and clean all air conditioning grills and wash as necessary.

     (b) Wipe down all exposed piping in stairwells and common areas.

6.   Annually

     (a) Wash interior and lenses and all light fixtures.

     (b) Clean all vertical surfaces not provided for above.

     (c) Damp wash all venetian blinds.



                                      E-3
<PAGE>   106

                                    EXHIBIT F

                      FORM OF NON-DISTURBANCE, ATTORNMENT,
                      ESTOPPEL AND SUBORDINATION AGREEMENT

         THIS NON-DISTURBANCE, ATTORNMENT, ESTOPPEL AND SUBORDINATION AGREEMENT
(this "AGREEMENT") is made and entered into as of ___________, 2000, by, between
and among WELLS FARGO BANK, NATIONAL ASSOCIATION (hereinafter referred to as
"BENEFICIARY" or "WELLS FARGO"), ("LESSEE"), and BOSTON PROPERTIES LIMITED
PARTNERSHIP, a Delaware limited partnership ("LESSOR").

                                    RECITALS

         A. Beneficiary is the owner and holder of that certain Promissory Note
in the principal sum of Thirty-Two Million and 00/100ths Dollars
($32,000,000.00) dated April 10, 2000 (the "NOTE") made by TOWER OAKS FINANCING
LLC, a Delaware limited liability company ("BORROWER");

         B. Lessor guarantied all of Borrower's obligations under the Note, that
certain Construction Loan Agreement dated as of April 10, 2000 by and between
Lessor, Beneficiary and Borrower (the "LOAN AGREEMENT") and all of the other
documents evidencing and securing the loan evidenced by the Note (collectively,
the "LOAN DOCUMENTS") pursuant to that certain Payment Guaranty Agreement dated
as of April 10, 2000 made by Lessor in favor of Beneficiary (the "PAYMENT
GUARANTY") and that certain Completion Guaranty Agreement dated as of April 10,
2000 made by Lessor in favor of Beneficiary (the "COMPLETION GUARANTY"; the
Payment Guaranty and the Completion Guaranty are herein sometimes collectively
referred to as the "GUARANTIES"); and

         C. The Guaranties are secured by an Indemnity Deed of Trust, Security
Agreement and Assignment of Leases and Rents (the "DEED OF TRUST") and an
Assignment of Leases and Rents (the "ASSIGNMENT"), each dated as of April 10,
2000, which Deed of Trust and Assignment constitute a lien or encumbrance on
that certain real property more particularly described in the attached Exhibit A
(the "PROPERTY").

         D. Lessee is the holder of a leasehold estate covering a portion of the
Property (the "DEMISED PREMISES") pursuant to the terms of that certain lease
dated ________________, 200_ and executed by Lessee and Lessor (the "LEASE"). A
true and correct copy of the Lease or recorded memorandum of Lease is attached
hereto as Exhibit B, or has previously been delivered to Beneficiary.

         E. Lessee, Lessor and Beneficiary desire to confirm their understanding
with respect to the Lease, the Assignment and the Deed of Trust.



                                      F-1
<PAGE>   107

                                    AGREEMENT

         1. So long as Lessee is not in default (beyond any period given Lessee
to cure such default) in the payment of rent or in the performance of any of the
terms, covenants or conditions of the Lease on Lessee's part to be performed,
Lessee's possession and occupancy of the Demised Premises shall not be
interfered with or disturbed by Beneficiary during the term of the Lease or any
extension thereof duly exercised by Lessee.

         2. Lessee hereby consents to the assignment by Lessor to Beneficiary of
the Lease, as set forth in the Deed of Trust and the Assignment. If the
interests of Lessor shall be transferred to and/or owned by Beneficiary by
reason of judicial foreclosure, power-of-sale foreclosure or other proceedings
brought by it, or by any other manner, including, but not limited to
Beneficiary's exercise of its rights under the Assignment, and Beneficiary
succeeds to the interest of the Lessor under the Lease, Lessee shall be bound to
Beneficiary under all of the terms, covenants and conditions of the Lease for
the balance of the remaining term thereof and any extension thereof duly
exercised by Lessee, with the same force and effect as if Beneficiary were the
Lessor under the Lease, and Lessee does hereby attorn to Beneficiary as its
lessor, said attornment to be effective and self-operative without the execution
of any further instruments on the part of any of the parties hereto immediately
upon Beneficiary's succeeding to the interest of the Lessor under the Lease;
provided, however, that Lessee shall be under no obligation to direct its
payment of rent to Beneficiary until Lessee receives written notice from
Beneficiary that it has succeeded to the interest of Lessor under the Lease or
that it has terminated the Lessor's right to collect rents as provided in the
Deed of Trust. The respective rights and obligations of Lessee and Beneficiary
upon such attornment, to the extent of the then remaining balance of the term of
the Lease and any such extension, shall be and are the same as now set forth
therein, it being the intention of the parties hereto for this purpose to
incorporate the Lease in this Agreement by reference with the same force and
effect as if set forth in full herein.

         3. If Beneficiary shall succeed to the interest of Lessor under the
Lease, Beneficiary shall, subject to the last sentence of this SECTION 3, be
bound to Lessee under all of the terms, covenants and conditions of the Lease;
provided, however, that Beneficiary shall not be:



                                      F-2
<PAGE>   108

                  (a) Liable for any act or omission of any prior lessor
(including Lessor); or

                  (b) Subject to any offsets, defenses or counterclaims which
Lessee might have against any prior lessor (including Lessor); or

                  (c) Bound by any rent, additional rent or advance rent which
Lessee might have paid for more than the current month to any prior lessor
(including Lessor) and all such rent shall remain due and owing notwithstanding
such advance payment; or

                  (d) Bound by any amendment or modification of the Lease made
without its consent and written approval; or

                  (e) Required to restore the building, complete any
improvements or otherwise perform the obligations of Lessor under the Lease in
the event of a foreclosure of the Deed of Trust or acceptance by Beneficiary of
a deed in lieu of foreclosure, in either instance prior to full restoration of
the building or completion of any improvements; or

                  (f) Liable under any circumstances for consequential damages
or for the ordinary negligence of Beneficiary or its agents.

         Neither Wells Fargo nor any other party who, from time to time, shall
be included in the definition of the term "BENEFICIARY" hereunder shall have any


                                      F-3

<PAGE>   109
liability or responsibility under or pursuant to the terms of this Agreement
after it ceases to own a fee interest in or to the Property.

         4. Subject to the terms of this Agreement (including, but not limited
to, those in SECTION 2 hereof), the Lease and the terms thereof are, and shall
at all times continue to be, subject and subordinate in each and every respect,
to the Deed of Trust and the terms thereof, and to any and all renewals,
modifications, extensions, substitutions, replacements and/or consolidations of
the Deed of Trust. Nothing herein contained shall be deemed or construed as
limiting or restricting the enforcement by Beneficiary of any of the terms,
covenants, provisions or remedies of the Deed of Trust or the Assignment,
whether or not consistent with the Lease.

         5. The term "BENEFICIARY" shall be deemed to include Wells Fargo and
all of its successors and assigns, including anyone who shall have succeeded to
Lessor's interest by, through or under judicial or power-of-sale foreclosure or
other proceedings brought pursuant to the Deed of Trust, or deed in lieu of such
foreclosure or proceedings, or otherwise.

         6. Lessor and Lessee certify to Beneficiary as follows: (a) that the
Lease is presently in full force and effect and unmodified or changed; (b) that
the term shall commence or did commence on ______________________, 200_, and
full rental will then accrue or is now accruing thereunder; (c) that all
conditions required under the Lease that could have been satisfied as of the
date hereof have been met; (d) that no rent under said Lease has been paid more
than thirty (30) days in advance of its due date; (e) that no default or event,
which with the giving of notice, passage of time, or both, would constitute a
default, exists under said Lease; (f) that the Lessee, as of this date, has no
charge, lien or claim of offset under said Lease or otherwise, against rents or
other charges due to become due thereunder; (b) that the Lease constitutes the
entire rental agreement between the parties and that Beneficiary shall have no
liability or responsibility with respect to any security deposit of Lessee; (h)
that the only persons, firms or corporations in possession of said leased
premises or having any right to the possession or use of said premises (other
than the record owner) are those holding under the Lease; and (i) that the
Lessee has no right or interest in or under any contract, option or agreement
involving the sale or transfer of the Demised Premises.

         7. In the absence of the prior written consent of Beneficiary, Lessee
agrees not to do any of the following: (a) (except for the prepayment of
operating expenses and security deposits) prepay the rent under the Lease for
more than one (1) month in advance, (b) enter into any agreement with the Lessor
to amend or modify the Lease; provided, however, that Beneficiary's consent
shall not be unreasonably withheld, conditioned or delayed, it being agreed that
in the event Beneficiary fails to respond to any written request for approval of
any such modification or amendment within (15) business days after its receipt
of such



                                      F-4
<PAGE>   110
written request, together with copies of such proposed modification or
amendment, the Beneficiary shall be deemed to have approved such modification or
amendment, (c) voluntarily surrender the Demised Premises or terminate the Lease
prior to the expiration date thereof set forth in the Lease, except as provided
by the Lease terms, (d) sublease or assign the Demised Premises (except with
respect to subleases of not more than one (1) full floor of the Building and are
for a term of not less than three (3) years; provided, however, that
Beneficiary's consent shall not be unreasonably withheld, conditioned or
delayed, it being agreed that in the event Beneficiary fails to respond to any
written request for approval of any such sublease or assignment within fifteen
(15) business days after its receipt of such written request, together with
copies of such proposed sublease or assignment, the Beneficiary shall be deemed
to have approved such sublease or assignment.

         8. In the event Lessor shall fail to perform or observe any of the
terms, conditions or agreements in the Lease, Lessee shall give written notice
thereof to Beneficiary and Beneficiary shall have the right (but not the
obligation) to cure such failure. Lessee shall not take any action with respect
to such failure under the Lease, including, without limitation, any action in
order to terminate, rescind or avoid the Lease or to withhold any rent
thereunder, for a period of thirty (30) days after receipt of such written
notice by Beneficiary; provided, however, that in the case of any default which
cannot with diligence be cured within said thirty (30) day period, if
Beneficiary shall proceed promptly to cure such failure and thereafter prosecute
the curing of such failure with diligence and continuity, the time within which
such failure may be cured shall be extended for such period as may be necessary
to complete the curing of such failure with diligence and continuity.

         9. So long as the loan evidenced by the Note (the "LOAN") is
outstanding, Lessee covenants to provide Beneficiary with all information,
including, but not limited to, evidence of payment of taxes and insurance (if
Lessee is obligated for such payments under the Lease) to which the Lessor may
be entitled under the Lease.

         10. So long as the Loan is outstanding, Beneficiary or its designee may
enter upon the Property at all reasonable times, upon twenty-four (24) hours
notice during normal working hours, to visit or inspect the Property and discuss
the affairs, finances and accounts of Lessee applicable to the Property or the
Lease at such reasonable times as Beneficiary or its designee may request;
provided, however, that (a) Lessee shall have the right to escort Beneficiary on
such inspection of the Property and (b) Beneficiary shall not unreasonably
interfere with Lessee's business operations.




                                      F-5
<PAGE>   111

         11. Lessee hereby represents and warrants that the Lease and this
Agreement have been duly authorized, executed and delivered by Lessee and
constitute legal, valid and binding instruments, enforceable against Lessee in
accordance with their respective terms, except as such terms may be limited by
bankruptcy, insolvency or similar laws affecting creditors' rights generally;
and (b) Beneficiary hereby represents that this Agreement have been duly
authorized, executed and delivered by and constitute legal, valid and binding
instruments, enforceable against Beneficiary in accordance with their respective
terms, except as such terms may be limited by bankrupty, insolvency or similar
laws affecting creditors' rights generally.

         12. Beneficiary represents that Beneficiary currently is the sole (a)
holder or beneficiary under Deed of Trust, and (b) holder of the Note and any
and all of the Loan Documents.

         13. This Agreement may not be modified orally or in any other manner
than by an agreement in writing signed by the parties hereto and their
respective successors in interest. This Agreement shall inure to the benefit of
and be binding upon the parties hereto, their successors and assigns.

         14. This Agreement may be executed in several counterparts, and all so
executed shall constitute one agreement, binding on all parties hereto,
notwithstanding that all parties are not signatories to the original or the same
counterpart.

         15. All notices or other communications required or permitted to be
given pursuant to the provisions hereof shall be in writing and shall be
considered as properly given if mailed by first class United States mail,
postage prepaid, registered or certified with return receipt requested, or by
delivering same in person to the intended addressee, or by prepaid telegram.
Notice so given in person or by telegram shall be effective upon its deposit.
Notice so given by mail shall be effective two (2) days after deposit in the
United States mail. Notice given in any other manner shall be effective only if
and when received by the addressee. For purposes of notice, the addresses of the
parties shall be:

         Lessor:           Boston Properties Limited Partnership
                                    c/o Boston Properties, Inc.
                                    800 Boylston Street
                                    Suite 400
                                    Boston, Massachusetts 02199
                                    Attention:   General Counsel



                                      F-6
<PAGE>   112
         Lessee:           Prior to the Lease Commencement Date:


                                    -------------------------------------------
                                    -------------------------------------------
                                    -------------------------------------------
                                    Attention:
                                               --------------------------------
                                    After the Lease Commencement Date:

                                    -------------------------------------------
                                    2600 Tower Oaks Boulevard, Suite _________
                                    Rockville, Maryland  20852
                                    Attention:
                                               --------------------------------

         Beneficiary:               Wells Fargo Bank, National Association
                                    c/o Real Estate Group
                                    2020 K Street, N.W., Suite 420
                                    Washington, D.C.  20006
                                    Attention:   Manager, Loan
                                                 Administration Department

provided, however, that any party shall have the right to change its address for
notice hereunder to any other location within the continental United States by
the giving of thirty (30) days' notice to the other parties in the manner set
forth hereinabove.

         16. In the event of any foreclosure of the Deed of Trust or any
conveyance in lieu of foreclosure, provided that the Lessee shall not then be in
default beyond any grace period under the Lease. Lessee shall not be made party
in any action or proceeding to remove or evict Lessee or to disturb its
possession, nor shall the leasehold estate of Lessee created by the Lease be
affected in any way, and the Lease shall continue in full force and effect as a
direct lease between Lessee and Beneficiary; provided, however, that Beneficiary
may join Lessee as a party in such action or proceeding if such joinder is
necessary under my statute of law for purposes of effecting the remedies
available to Beneficiary under the Deed of Trust or the other Loan Documents.

         17. Beneficiary agrees that the Note and/or Deed of Trust shall in no
manner become a lien on any trade fixture, business equipment, signs or other
personal property or goodwill of Lessee beyond Lessor's interest, if any,
therein.

         18. Beneficiary acknowledges and agrees that in no event shall Lessee
be liable for any of the obligations of Lessor under the Deed of Trust or any
of the other Loan Documents.


                                      F-7
<PAGE>   113
         19. Beneficiary agrees to make insurance proceeds it receives in
connection with any casualty on the Property available for restoration, all in
accordance with and subject to the terms and conditions contained in the Deed
of Trust.


                                      F-8
<PAGE>   114



         IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the day and year first above written.

                                       OTG SOFTWARE, INC.

                                       By:
                                           -----------------------------------
                                            Name:
                                            Title:


STATE OF                            )       ss:
         --------------------------
COUNTY OF                           )
          -------------------------


         I, a Notary Public in and for the aforesaid jurisdiction, do hereby
certify that _______________________, who is personally well known to me as, or
satisfactorily proven to be, the person named as _____________ of in the
foregoing Non-Disturbance, Attornment, Estoppel and Subordination Agreement
bearing date as of the ____ day of ________, 200_, personally appeared before me
in the said jurisdiction, and by virtue of the authority vested in him or her by
said Agreement, acknowledged the same to be the act and deed of said
organization, and delivered the same as such.

         GIVEN under my hand and official seal this ____ day of _________, 200_.


                                  ---------------------------------------------
                                  Notary Public

My Commission Expires:
                       -------------------------------


                       [SIGNATURES CONTINUED ON NEXT PAGE]





                                      F-9
<PAGE>   115

                                  BOSTON PROPERTIES LIMITED
                                  PARTNERSHIP, a Delaware limited
                                  partnership

                                  By:  Boston Properties, Inc., its
                                       General Partner


                                       By:
                                           ------------------------------------
                                           Name:
                                           Title:


DISTRICT OF COLUMBIA       )        ss:

         I, a Notary Public in and for the aforesaid jurisdiction, do hereby
certify that __________________________, who is personally well known to me as,
or satisfactorily proven to be, the person named as ______________ of Boston
Properties, Inc., the General Partner of Lessor in the foregoing
Non-Disturbance, Attornment, Estoppel and Subordination Agreement, bearing date
as of the ___ day of _________, 2000, personally appeared before me in the said
jurisdiction, and acknowledged the same to be the act and deed of Lessor, and
delivered the same as such.

         GIVEN under my hand and official seal this ____ day of ____________,
2000.


                                  ---------------------------------------------
                                  Notary Public


My Commission Expires:
                       ------------------------------



                       [SIGNATURES CONTINUED ON NEXT PAGE]



                                      F-10
<PAGE>   116

                                  WELLS FARGO BANK, NATIONAL
                                  ASSOCIATION


                                  By:
                                      -----------------------------------------
                                      Name:
                                      Title:

DISTRICT OF COLUMBIA                )  ss:

         I, a Notary Public in and for the aforesaid jurisdiction, do hereby
certify that __________________, who is personally well known to me as, or
satisfactorily proven to be, the person named as __________ Vice President of
Wells Fargo Bank, National Association in the foregoing Non-Disturbance,
Attornment, Estoppel and Subordination Agreement bearing date as of the ____ day
of _________, 2000, personally appeared before me in the said jurisdiction, and
acknowledged the same to be the act and deed of Wells Fargo Bank, National
Association, and delivered the same as such.

         GIVEN under my hand and official seal this ____ day of _________, 2000.


                                  ---------------------------------------------
                                  Notary Public

My Commission Expires:
                        -----------------------------------




                                      F-11
<PAGE>   117




                                    EXHIBIT A

                        LEGAL DESCRIPTION OF THE PROPERTY





                                      F-12
<PAGE>   118




                                    EXHIBIT B

                  COPY OF LEASE OR RECORDED MEMORANDUM OF LEASE






                                      F-13

<PAGE>   119




                                    Exhibit G




                                    SUBLEASE

                                     Between

                               OTG SOFTWARE, INC.

                                       and





                          ----------------------------




                                      xxiv




<PAGE>   120


                                Table of Contents


<TABLE>
<CAPTION>
                                                                                     Page
                                                                                     ----

<S>      <C>                                                                         <C>
1.       Subleased Premises and Term................................................  2
2.       Subleased Premises Responsibilities........................................  3
             a.   Permits...........................................................  3
             b.   Delivery and Acceptance...........................................  3
             c.   Subtenant's Installations.........................................  4
3.       Rent.......................................................................  4
             a.   Basic Rent........................................................  4
             b.   Additional Charges................................................  5
             c.   Payment of Rent...................................................  6
4.       Permitted Use..............................................................  6
5.       Incorporation of Lease.....................................................  6
6.       Transmittal of Notices and Demands.........................................  8
7.       Landlord's Consent to Certain Acts.........................................  8
8.       Sublandlord's Right to Cure Subtenant's Default............................  9
9.       Assignment of Sublease.....................................................  9
10.      Eminent Domain, Loss by Casualty...........................................  10
11.      Notice and Demands.........................................................  10
12.      Alterations to Subleased Premises..........................................  11
13.      [OPTIONAL] Parking.........................................................  11
14.      Brokerage Fees.............................................................  12
15.      Subtenant Authority to Execute Lease.......................................  12
16.      Security Deposit...........................................................  12
17.      Consent of Landlord........................................................  14
18.      Quiet Enjoyment............................................................  14
19.      Miscellaneous..............................................................  15
             a.   No Offer..........................................................  15
             b.   No Partnership....................................................  15
             c.   Time of the Essence...............................................  15
             d.   Separability......................................................  16
</TABLE>



                                      xxiv
<PAGE>   121


<TABLE>
<S>          <C>                                                                      <C>
             e.   Counterparts......................................................  16
             f.   Merger............................................................  16
Exhibit A         Lease.............................................................  20
Exhibit B         Space Plan Depicting Subleased Premises...........................  21
</TABLE>



                                      xxv
<PAGE>   122

                                       1



                                    SUBLEASE


         THIS SUBLEASE ("SUBLEASE") IS MADE AS OF THE ____ DAY OF
____________________, 200__, BY AND BETWEEN OTG SOFTWARE, INC., A
____________________ CORPORATION ("SUBLANDLORD"), AND ________________________ A
_______________, ("SUBTENANT").

                                    RECITALS:

         A. Sublandlord is the "Tenant" under a certain office lease dated
_____________ (the "Lease"), from Boston Properties Limited Partnership, a
Delaware limited partnership ("Landlord"), by which it has leased certain space
on the ____________ (_____) floors ("Leased Premises") of the building located
at 2600 Tower Oaks Boulevard, Rockville, Maryland (the "Building").

         B. A true and correct copy of the Lease is attached to and made a part
of this Sublease as Exhibit A.

         C. Subtenant desires to sublease from Sublandlord, and Sublandlord
desires to sublease to Subtenant ______ rentable square feet of space located on
the ________ (______) floor of the Building (the "Subleased Premises"), which
Subleased Premises is shown as the cross-hatched area on the space plan attached
to and made a part of this Sublease as Exhibit B.


<PAGE>   123

                                       2



         NOW, THEREFORE, in consideration of the rents, covenants and agreements
herein contained, IT IS HEREBY AGREED AS FOLLOWS:

         1. SUBLEASED PREMISES AND TERM. Sublandlord hereby subleases the
Subleased Premises to Subtenant and Subtenant hereby subleases the Subleased
Premises from Sublandlord upon and subject to the terms, covenants, rentals and
conditions herein set forth, for a term (the "Term") of ______ (___) commencing
on the 1st day of __________________, 200__ (the "Sublease Commencement Date")
and expiring on ___________________ (the "Sublease Expiration Date"); provided,
however that if the Lease shall be terminated for any reason prior to the
Sublease Expiration Date, then this Sublease shall expire on the termination
date of the Lease. If Sublandlord shall be unable to deliver possession of the
Subleased Premises to Subtenant on __________________ (the "Anticipated Sublease
Commencement Date"), for any reason, Sublandlord shall not be subject to any
liability for the failure to tender possession on said date. In such event, the
rent covenanted to be paid herein shall not commence and the Sublease
Commencement Date shall not occur until possession of the Subleased Premises is
tendered to Subtenant. No such failure to give possession on the Anticipated
Sublease Commencement Date shall in any other respect affect the validity of
this Sublease or the obligations of Subtenant hereunder, nor shall the same be


<PAGE>   124

                                       3


construed to extend the Term, which shall in all events expire on the Sublease
Expiration Date.

         For purposes of this Sublease, the term "Sublease Year" shall mean each
twelve (12) month period during the Term beginning on the first day of the month
coincident with or next following the Sublease Commencement Date and each
subsequent anniversary thereof; provided, that the last Sublease Year of the
Term shall end on the Sublease Expiration Date and if the Sublease Commencement
Date is not the first day of a calendar month, the period between the Sublease
Commencement Date and the first day of the next calendar month shall be included
in the first Sublease Year.

         2. SUBLEASED PREMISES RESPONSIBILITIES.

                  (a) PERMITS. Subtenant shall be responsible for obtaining all
permits or licenses necessary for its lawful occupancy of the Subleased
Premises. This requirement shall not relieve Subtenant of its liability for
Basic Rent (as defined in Section 3(a)) and Additional Charges (as defined in
Section 3(b)) from the Sublease Commencement Date in the event all said permits
to be obtained by Subtenant have not been acquired prior thereto.


<PAGE>   125

                                       4



                  (b) DELIVERY AND ACCEPTANCE. Subtenant agrees to accept the
Subleased Premises in its "AS-IS" condition as of the date of this Sublease.

                  (c) SUBTENANT'S INSTALLATIONS. Subtenant, at its expense,
shall install its telephone system, computer equipment and furniture and
fixtures in the Subleased Premises.

         3. RENT. Commencing on the Sublease Commencement Date, Subtenant
covenants and agrees to pay to Sublandlord as rent for the Subleased Premises:

                  (a) BASIC RENT. A basic rent of _____________________ and
____/100 Dollars ($___________) per annum ("Basic Rent") payable in equal
monthly installments of monthly Basic Rent in the amount of
____________________________ and No/100 Dollars ($__________). Subtenant shall
pay the first monthly installment of Basic Rent upon execution of this Sublease.
Subtenant shall pay the remaining monthly installments of Basic Rent in advance
without prior demand, and without deduction, abatement, recoupment or set-off of
any kind, upon the first day of each and every calendar month throughout the
Term.


<PAGE>   126

                                       5



                           On the first day of the second Sublease Year and on
the first day of each Sublease Year thereafter, the Basic Rent shall be
increased as follows: ________________.

                  (b) ADDITIONAL CHARGES. Additional Charges, upon demand
therefor by Sublessor, consisting of:

                           (i) ___________________________________ percent
(_____%) ("Subtenant's Share") of the increase in "Operating Expenses" (as
defined in Article IV of the Lease) during each calendar year over the Operating
Expenses for the "Base Year" (as defined in Article IV of the Lease), which
increases in Operating Expenses shall commence on the first day of the
______________ Sublease Year, and shall be billed by Sublandlord and payable by
Subtenant in the same manner as set forth in Article IV of the Lease;

                           (ii) The actual cost to Sublandlord of heating and
air conditioning supplied to the Subleased Premises after normal Building
operating hours at Subtenant's request, pursuant to Section 14.1 of the Lease,
which amounts shall be payable by Subtenant to Sublandlord within ten (10) days
after delivery to Subtenant of a bill therefor; and


<PAGE>   127

                                       6



                           (iii) Any other payment (other than Basic Rent)
required to be paid by Subtenant to Sublandlord under the terms of this
Sublease.

                  (c) PAYMENT OF RENT. Payment of Basic Rent and Additional
Charges shall be paid in lawful money of the United States to Sublandlord
"Attention: __________________________ at the address designated in Section 11
hereof, or as otherwise designated from time to time by written notice from
Sublandlord to Subtenant. The obligation to pay Basic Rent and/or Additional
Charges hereunder is independent of each and every other covenant and agreement
contained in this Sublease except as specifically set forth herein.

         4. PERMITTED USE. Subtenant shall use and occupy the Subleased Premises
for general office purposes and for no other use or purposes.

         5. INCORPORATION OF LEASE. Except as herein otherwise expressly
provided, all of the terms of the Lease as they pertain to the Subleased
Premises are hereby incorporated into and made a part of this Sublease as if
stated at length herein, and Subtenant accepts this Sublease subject to, and
hereby, during the Term of this Sublease, assumes all of the terms, covenants,
conditions and agreements contained in the Lease with respect to

<PAGE>   128

                                       7


the Subleased Premises, to be performed by Sublandlord thereunder. The parties
hereto agree that subject to the provisions of this Sublease, wherever the words
"Leased Premises" or words of similar import appear in the Lease, the same shall
be deemed to mean the Subleased Premises and wherever the words "Landlord" and
"Tenant" appear in the Lease, the words shall be deemed to refer to Sublandlord
and Subtenant respectively, so that, subject to the provisions of this Sublease
and with respect only to the Subleased Premises, Sublandlord shall have the
rights and powers of the Landlord under the Lease, and Subtenant shall have and
does hereby agree to be bound by and accept all the rights, powers, duties and
obligations of the Tenant under the Lease; provided, however, that
notwithstanding the foregoing, Sublandlord shall have no obligation to perform
or furnish any of the work, services, repairs or maintenance undertaken to be
made by Landlord under the Lease, or any other term, covenant or condition
required to be performed by Landlord under the Lease. Subtenant covenants and
agrees that it shall do nothing which shall have the effect of creating a breach
of any of the terms, covenants and conditions of the Lease. In the event that
Landlord shall fail or refuse to comply with any of the respective provisions of
the Lease, Sublandlord shall have no liability on account of any such failure or
refusal. Sublandlord hereby agrees to cooperate with and execute, all at
Subtenant's expense, all instruments and supply information reasonably required
by Subtenant in order to enforce such compliance.


<PAGE>   129

                                       8


Subtenant hereby agrees to indemnify and hold Sublandlord harmless of and from
any and all damages, liabilities, obligations, costs, claims, losses, demands,
and expenses, including reasonable attorneys' fees, which may be incurred by
Sublandlord in or as a result of such cooperation and execution. In
amplification and not in limitation of the foregoing and without any allowance
to Subtenant or other reduction or adjustment of Basic Rent and/or Additional
Charges, Sublandlord shall not be responsible for furnishing electrical,
elevator, heating, air conditioning, cleaning, window washing, or other
services, nor for any maintenance or repairs in or to the Subleased Premises or
the Building of which it is a part or to any of the facilities or equipment
therein.

         The following (a) sections of the Lease shall not be applicable to this
Sublease: Sections 1.1, 1.3, 2.2, 2.3, 2.4, 3.1, 3.2, 3.3, 4.1(c), 5.1, 10.2,
15.6, 24.1, 25.3, 25.20, 26.1, 26.2, 26.3, 27.1, 27.2, 27.3, 27.4 and 27.5; and
(b) provisions of the Lease shall not be applicable to this Sublease: Rider No.
1, Exhibit B, Exhibit D, and Exhibit F.

         6. TRANSMITTAL OF NOTICES AND DEMANDS. Sublandlord shall promptly
transmit to Landlord any notice or demand received from Subtenant and shall
promptly transmit to Subtenant any notice or demand received from Landlord.
Subtenant shall promptly transmit

<PAGE>   130

                                        9



to Sublandlord any notice or demand received from Landlord or any other party
relating to the Subleased Premises.

         7. LANDLORD'S CONSENT TO CERTAIN ACTS. Subtenant agrees that in any
case where the provisions of the Lease or this Sublease require the consent or
approval of Landlord or Sublandlord prior to the taking of any action, it shall
be a condition precedent to the taking of such action that the prior consent or
approval of Landlord shall have been obtained if Landlord's consent must be
obtained under the Lease in such cases. Subtenant agrees that Sublandlord shall
not have any duty or responsibility with respect to obtaining the consent or
approval of Landlord when the same is required under the terms of the Lease,
other than the transmission by Sublandlord to Landlord of Subtenant's request
for such consent or approval.

         8. SUBLANDLORD'S RIGHT TO CURE SUBTENANT'S DEFAULT. Subtenant shall not
do or suffer or permit anything to be done which would cause the Lease to be
terminated or forfeited by virtue of any rights of termination or forfeiture
reserved or vested in Landlord or by law or in equity. If Subtenant shall
default in the performance of any of its obligations under this Sublease or
under the Lease, Sublandlord, without being under any obligation to do so and
without thereby waiving such default, may remedy such default for the account
and at the expense of Subtenant upon

<PAGE>   131

                                       10



prior notice. If Sublandlord makes any expenditures or incurs any obligation for
the payment of money in connection therewith, such sums paid or obligations
incurred shall be deemed to be Additional Charges hereunder and shall be paid to
Sublandlord by Subtenant on demand.

         9. ASSIGNMENT OF SUBLEASE. Notwithstanding anything to the contrary in
Article VII of the Lease, Subtenant shall not assign, mortgage or encumber this
Sublease, nor sublet, nor suffer or permit the Subleased Premises or any part
thereof to be used by others except with the prior written consent of
Sublandlord and Landlord, which may be granted or withheld in their sole and
absolute discretion.

         10. EMINENT DOMAIN, LOSS BY CASUALTY. Notwithstanding anything to the
contrary in Articles XVII and XVIII of the Lease, in the event of any taking by
eminent domain or damage by fire or other casualty to the Subleased Premises
thereby rendering the Subleased Premises wholly or in part untenantable,
Subtenant shall acquiesce in and be bound by any action taken by or agreement
entered into between Landlord and Sublandlord with respect thereto.

         11. NOTICE AND DEMANDS. All notices or demands under this Sublease
shall be in writing and shall be sent pursuant to


<PAGE>   132
                                       11



Section 25.6 of the Lease, to the following addresses or such other address as
either of the parties may designate by written notice:

         If To Sublandlord:
                                        ---------------------------------------
                                        ---------------------------------------
                                        ---------------------------------------
                                        ---------------------------------------
                                        Attn:
                                               --------------------------------
                                               --------------------------------

         with a copy to:
                                        ---------------------------------------
                                        ---------------------------------------
                                        ---------------------------------------
                                        ---------------------------------------
                                        Attn:
                                               --------------------------------


         If To Subtenant:               Before occupancy of Subleased Premises:

                                        ---------------------------------------
                                        ---------------------------------------
                                        ---------------------------------------
                                        Attn:
                                               --------------------------------

                                        After occupancy of Subleased Premises:

                                        ---------------------------------------
                                        ---------------------------------------
                                        ---------------------------------------
                                        Attn:
                                               --------------------------------

         12. ALTERATIONS TO SUBLEASED PREMISES. Notwithstanding anything to the
contrary in Article IX of the Lease, Subtenant covenants at all times during the
Term not to make any alterations or additions to the Subleased Premises of any
nature whatsoever without the prior written consent of Sublandlord and
<PAGE>   133

                                       12



Landlord, which may be granted or withheld in their sole and absolute
discretion.

         13. [OPTIONAL] PARKING. Notwithstanding anything to the contrary in
Article XXIV of the Lease, Subtenant shall have the right to use up to _________
(___) parking spaces on a non-assigned basis per ___________ square feet of
Rentable Area. The parking contracts shall be with the garage operator and shall
contain the same terms as are usually contained in contracts with other
customers of the operator and the monthly rental shall be the monthly rate the
operator charges other monthly parking customers, which is currently $________
per unreserved space per month and shall increase or decrease as the prevailing
monthly parking rates increase or decrease from time to time.

         14. BROKERAGE FEES. The parties hereto represent and warrant to each
other that they have not dealt with any broker other than
________________________________________. ___________________ shall pay said
broker a brokerage commission pursuant to a separate agreement between
Sublandlord and said broker in connection with this Sublease. Each party hereto
agrees to indemnify, defend and hold the other party harmless against any claim
or liability for a commission by any broker, arising by reason of a breach by
the indemnifying party of the aforesaid representation and warranty.


<PAGE>   134

                                       13



         15. SUBTENANT AUTHORITY TO EXECUTE LEASE. Subtenant represents and
warrants that this Sublease has been duly authorized, executed and delivered by
and on behalf of the Subtenant and constitutes the valid and binding agreement
of the Subtenant in accordance with the terms hereof.

         16. SECURITY DEPOSIT. Subtenant has deposited with Sublandlord
simultaneously with the execution of Sublease, the sum of
_____________________________ and ____/100 Dollars ($_________) as a deposit
(the "Security Deposit") to secure the prompt performance of Subtenant's
obligations hereunder. The Security Deposit may be commingled with Sublandlord's
general funds, if permitted by law. Sublandlord shall have the right, but shall
not be obligated, to apply all or any portion of the Security Deposit to cure
any default, in which event Subtenant shall be obligated to deposit with
Sublandlord the amount necessary to restore the Security Deposit to its original
amount within five (5) days after written notice from Sublandlord. To the extent
not forfeited or otherwise used as provided herein, and provided the Subleased
Premises are vacated in good condition, ordinary wear and tear and damage by
fire or other casualty excepted, as described in Section 26, the Security
Deposit shall be returned, without interest, to Subtenant within thirty (30)
days after the expiration or other termination of


<PAGE>   135

                                       14



this Sublease. Sublandlord may deliver the Security Deposit to any assignee of
Sublandlord's interest in this Sublease, whereupon Sublandlord shall be
discharged from any further liability with respect to the Security Deposit. This
provision shall apply also to any and all subsequent transferrers of the
Sublandlord's interest in this Sublease.

                  If the Subtenant fails to take possession of the Subleased
Premises as required by this Sublease, the Security Deposit shall not be deemed
liquidated damages and Sublandlord's use of the Security Deposit pursuant to
this paragraph shall not preclude Sublandlord from recovering from Subtenant all
additional damages incurred by Sublandlord.

         17. CONSENT OF LANDLORD. The written consent of Landlord to this
Sublease is required under the terms of the Lease, and neither party hereto
shall be bound hereby until said consent is fully executed and delivered among
the parties. This Sublease is contingent, in its entirety, upon Sublandlord's
obtaining Landlord's consent to this Sublease. If the aforesaid consent has not
been obtained by ___________________, _____, then either party may terminate
this Sublease by written notice to the other given before such consent is
obtained. In the event of such termination, Sublandlord shall return any
Security Deposit and the first monthly installment of Basic Rent paid by
Subtenant
<PAGE>   136

                                       15



pursuant to Section 3(a) hereof, and the parties shall thereupon be relieved of
any and all liability hereunder. Upon the execution hereof, Sublandlord will
promptly submit this Sublease to Landlord for its consent. Sublandlord shall use
reasonable efforts to obtain such consent within fifteen (15) business days
after the execution of this Sublease by both parties.

         18. QUIET ENJOYMENT. So long as Subtenant shall observe and perform all
of the covenants and agreements binding on it hereunder, Subtenant shall at all
times during the Term hereof peacefully and quietly have and enjoy possession of
the Subleased Premises without hindrance by Sublandlord, subject to the terms of
this Sublease.

         19. MISCELLANEOUS.

                  (a) NO OFFER. Submission of this instrument for examination
shall not constitute a reservation of or option for the Subleased Premises or in
any manner bind Sublandlord and no Sublease or obligation on Sublandlord shall
arise until this instrument is signed and delivered by Sublandlord and
Subtenant; provided, however, the execution and delivery by Subtenant of this
Sublease to Sublandlord shall constitute an irrevocable offer by Subtenant to
sublease the Subleased Premises on the
<PAGE>   137

                                       16



terms and conditions herein contained, which offer may not be revoked for
forty-five (45) days after such delivery.

                  (b) NO PARTNERSHIP. Nothing contained in this Sublease shall
be deemed or construed by the parties hereto or by any third party to create the
relationship of principal and agent, partnership, joint venturer or any
association between Sublandlord and Subtenant, it being expressly understood and
agreed that no provisions contained in this Sublease or any act of the parties
hereto shall be deemed to create any relationship between Sublandlord and
Subtenant other than the relationship of landlord and tenant.

                  (c) TIME OF THE ESSENCE. Time is of the essence of this
Sublease and of each and all provisions hereof.

                  (d) SEPARABILITY. The legal invalidity of any provision of
this Sublease shall not impair or affect in any manner the validity,
enforceability or effect of the rest of this Sublease.

                  (e) COUNTERPARTS. This Sublease may be executed in several
counterparts, all of which shall constitute one and the same document.



<PAGE>   138
                                       17


                  (f) MERGER. All understandings and agreements, oral or
written, heretofore made between the parties hereto are merged in this Sublease,
which alone fully and completely expresses the agreement between Sublandlord and
Subtenant.
<PAGE>   139

                                       18



         IN WITNESS WHEREOF, the parties hereto have duly executed this Sublease
the day and year first above written.

ATTEST/WITNESS:                         SUBLANDLORD:
                                           OTG SOFTWARE, INC., a
                                           _______________ corporation

                                           By:                           (SEAL)
                                                -------------------------


ATTEST/WITNESS:                         SUBTENANT:

                                           ------------------------------------

                                           By:                           (SEAL)
                                                -------------------------


<PAGE>   140

                                       19



                               CONSENT OF LANDLORD

Boston Properties Limited Partnership, as Landlord under that certain Lease
Agreement with OTG Software, Inc. ("Tenant"), dated as of _______________, (the
"Lease"), respecting premises in the seven-story office building located at 2600
Tower Oaks Boulevard, Rockville, MD hereby acknowledges and consents to the
execution and delivery of the attached Agreement of Sublease (the "Sublease")
dated ___________, 200_, between Tenant and ___________________________, a
_______________ corporation ("Sublessee").

Notwithstanding the foregoing acknowledgment and consent, (i) Landlord is not,
and shall not be nor become, a party to the Sublease, (ii) Landlord's consent
does not and shall not create any contractual liability, obligation or duty on
the part of Landlord to Sublessee or in any manner affect the rights and
obligations of Landlord and Tenant under the Lease, (iii) Landlord's consent
does not and shall not mean or imply that Landlord makes, has made or will make
to Sublessee any of the representations or certifications set forth explicitly
or incorporated by reference in the Sublease, (iv) Landlord's consent does not
and shall not impose nor create any additional burden or obligation on Landlord
to Tenant and does not modify or alter Landlord's obligations to Tenant under
the Lease and (v) Tenant is not and shall not be relieved of or released from
any liability for the performance of the terms, conditions, covenants,
obligations, and duties of Tenant under the Lease, whether occurring prior or
subsequent to the effective date of the Sublease, including, without limitation,
the obligation to pay rent under the Lease, and Tenant shall pay directly to
Landlord all rent and other sums due to Landlord under the Lease.

Landlord's consent to the Sublease shall not mean that Landlord has reviewed and
approved any plans for Sublessee's space as required pursuant to the terms of
the Sublease and the Lease. Landlord shall not review any plans for Sublessee's
space unless and until Sublessee and Tenant shall have provided Landlord with
<PAGE>   141
                                       20



evidence that any and all plans for Sublessee's space conform to and comply with
the requirements of the Lease.


                              Boston Properties Limited Partnership
                              a Delaware limited partnership

                              BY:   Boston Properties, Inc., a Delaware
                                    corporation, its sole general partner


Date:                     By:
       ---------------        -------------------------------------------------
                                    Raymond A. Ritchey
                                    Executive Vice President

<PAGE>   142





                                   EXHIBIT A

                                     LEASE

                                  [RECITAL B]




<PAGE>   143





                                   EXHIBIT B

                              EXISTING SPACE PLAN

                                  [RECITAL C]





                 [cross-hatched and labeled Subleased Premises]
                      [attach floor plans of ______ floor]