<PAGE>

                                                                   Exhibit 10.16

                                    SUBLEASE



                                     between



                               DOVER CORPORATION,

                                  as Sublessor,



                                       and



                              ONESOFT CORPORATION,

                                  as Sublessee



                          Dated as of February 23, 1999
<PAGE>

                                TABLE OF CONTENTS
                                -----------------

                                                                           Page
                                                                           ----
ARTICLE 1     Definitions..................................................  1
ARTICLE 2     Sublease of the Subleased Premises: Use: Term................  2
ARTICLE 3     Rent/Electricity Charge......................................  3
ARTICLE 4     Incorporation of Master Lease................................  4
ARTICLE 5     Notices......................................................  6
ARTICLE 6     Right of Sublessor to Cure Sublessee's Defaults..............  7
ARTICLE 7     Consents and Approvals of Sublessor..........................  8
ARTICLE 8     Brokerage....................................................  9
ARTICLE 9     Consent of Prime Landlord....................................  9
ARTICLE 10    Insurance; Alterations; Restoration.......................... 10
ARTICLE 11    Notices...................................................... 10
ARTICLE 12    Miscellaneous................................................ 11
<PAGE>

     THIS AGREEMENT OF SUBLEASE (this "Sublease") made as of this 23rd day of
February, 1999, by and between DOVER CORPORATION, a Delaware corporation, having
an address at 280 Park Avenue, New York, New York 10017 (the "Sublessor"), and
ONESOFT CORPORATION, a Delaware corporation, having an address at 7010 Little
River Turnpike, Suite 460, Annandale, Virginia 22003 (the "Sublessee").

                                  WITNESSETH:
                                  ----------

     WHEREAS, the Sublessor is presently the tenant under that certain lease
dated December 20, 1996 (the "Master Lease") by and between Sablons Investors,
Inc., a New York corporation, predecessor in interest to Boston Properties
Limited Partnership, a Delaware limited partnership, as landlord (the "Prime
Landlord"), and the Sublessor, as tenant, covering the entire 34th floor in the
building known as 280 Park Avenue, New York, New York (the "Building"); and

     WHEREAS, the Sublessee desires to sublease from the Sublessor and the
Sublessor is willing to sublease to the Sublessee a portion of the 34th floor
leased under the Master Lease as identified on Exhibit A attached hereto and
                                               ---------
made a part hereof, together with all fixtures, equipment, improvements and
installations attached thereto on the date hereof (collectively, the "Subleased
Premises"), and all the appurtenances, rights and privileges belonging or
relating to the Subleased Premises, or any portion thereof.

     NOW, THEREFORE, in consideration of the premises and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the Sublessor and the Sublessee, for themselves, their successors
and permitted assigns, hereby covenant and agree as follows:

                              ARTICLE 1 Definitions
                              ---------------------


     Section 1.01. Except as otherwise specified or as the context may otherwise
require, the following terms shall have the respective meanings set forth below
for all purposes of this Sublease, and the definitions of such terms are equally
applicable both to the singular and the plural forms thereof:

     Building shall have the meaning set forth in the first WHEREAS clause.
     --------

     Commencement Date shall have the meaning set forth in Section 2.03.
     -----------------

     Electricity Charge shall have the meaning set forth in Section 3.02.
     ------------------

     Fixed Rent means $212,500.00 per annum.
     ----------

     Master Lease shall have the meaning set forth in the first WHEREAS clause.
     ------------

     PMR means Prime Manhattan Realty.
     ---

     Prime Landlord shall have the meaning set forth in the first WHEREAS
     --------------
clause.
<PAGE>

     Security Deposit shall have the meaning set forth in Section 3.04.
     ----------------

     Studley means Julien J. Studley, Inc.
     -------

     Sublease Expiration Date means the day prior to the fifth anniversary of
     ------------------------
the Commencement Date.

     Sublease Interest Rate means fifteen percent (15 %) per annum.
     ----------------------

     Subleased Premises shall have the meaning set forth in the second WHEREAS
     ------------------
clause.

     Term shall have the meaning set forth in Section 2.03.
     ----

             ARTICLE 2 Sublease of the Subleased Premises: Use: Term
             -------------------------------------------------------

     Section 2.01. The Sublessor hereby subleases, and the Sublessee hereby
hires and takes from the Sublessor, the Subleased Premises, subject to the
terms, provisions, covenants and conditions of this Sublease.

     Section 2.02. The Subleased Premises shall be used only for the purposes
permitted by the Master Lease, and for no other use or purpose.

     Section 2.03. The term of this Sublease (the "Term") shall commence on the
day after the Prime Landlord's consent is obtained pursuant to Article 9 hereof
(the "Commencement Date"). The Term shall expire on the Sublease Expiration
Date, unless it shall sooner cease and expire as hereinafter provided. The Term
of this Sublease shall not be extended due to delays in obtaining the Prime
Landlord's consent, or for any other reason.

     Section 2.04. The Sublessee acknowledges that it has inspected the
Subleased Premises and accepts the same in its "as is" condition on the date
hereof, subject to ordinary wear, tear and use between the date hereof and the
Commencement Date, and that the Sublessor shall have no obligation whatsoever to
(a) make any alterations, improvements or repairs, (b) install any fixtures or
equipment or (c) render any services to make the Building or the Subleased
Premises ready or suitable for the Sublessee's use or occupancy. The Sublessee
shall be solely responsible for any cost and expense incurred in connection with
any work or services performed in preparation for the Sublessee's use and
occupancy of the Subleased Premises.

     Section 2.05. If the Master Lease terminates for any reason whatsoever
prior to the date on which this Sublease is scheduled to expire, this Sublease
shall thereupon terminate immediately. The Sublessor shall not be liable to the
Sublessee by reason of any such termination and thereafter shall have no further
obligations of any kind whatsoever to the Sublessee.

     Section 2.06. Upon the scheduled expiration or termination of this
Sublease, or upon any earlier termination of this Sublease, the Sublessee shall
peaceably and quietly leave and surrender to the Sublessor the Subleased
Premises broom clean, in good condition and repair,

                                       2
<PAGE>

ordinary wear and tear excepted. The Sublessee's obligations under this Section
2.06 shall survive the expiration of the Term or any earlier termination of this
Sublease.

     Section 2.07.  If the Sublessor is unable to give possession of the
Subleased Premises on the Commencement Date for any reason whatsoever including,
but not limited to, the continuing possession of any other subtenant or person
or the failure or delay of the Prime Landlord in granting its consent to this
Sublease, the Sublessor shall not be liable for the failure to give such
possession, nor shall such failure be deemed to extend the Term. In such event,
this Sublease shall continue in full force and effect; provided, however, that
Fixed Rent shall abate until the Sublessor gives the Sublessee written notice
that the Subleased Premises are available for occupancy.

                        ARTICLE 3 Rent/Electricity Charge
                        ---------------------------------

     Section 3.01. The Sublessee hereby covenants and agrees to pay to the
Sublessor the Fixed Rent from the Commencement Date until the expiration or
sooner termination of the Term, payable in equal monthly installments of
$17,708.34 in advance on the first day of each month during the Term hereof,
without notice or demand and without abatement, deduction or set-off of any
amount whatsoever. In addition, the Sublessee hereby covenants and agrees to pay
additional rent (as such term is defined in the Master Lease) at the times and
in the manner set forth in the Master Lease as amended by this Sublease. If the
Commencement Date shall not occur on the first day of a month, the first month's
Fixed Rent and additional rent shall be prorated in the manner set forth in the
last sentence of Section 2.1 of the Master Lease.

     Section 3.02. In addition to the Fixed Rent specified in Section 3.01 of
this Sublease, from the Commencement Date the Sublessee shall also pay to the
Sublessor without notice or demand and without abatement, deduction or set-off
of any amount whatsoever, the sum of $2.75 per square foot (or $11,687.50 per
annum) (the "Electricity Charge") for electrical energy consumed on the
Subleased Premises during the Term hereof in equal monthly installments of
$973.96 in advance on the first day of each month during the Term hereof. The
Electricity Charge for the initial month of occupancy shall be pro rated if the
Commencement Date is not the first day of a month. At any time during the Term
at the Sublessor's request, the Sublessee's consumption of electrical energy in
the Subleased Premises shall be determined by a separate survey of the Subleased
Premises (excluding any other space demised under the Master Lease) by a
reputable independent electrical engineer to be selected by the Sublessor whose
fees or charges shall be paid equally by the Sublessor and the Sublessee.
Notwithstanding anything in this Sublease to the contrary, the amount that the
Sublessee shall be obligated to pay for electricity shall be based upon such
survey and similar periodic surveys made from time to time (but not more often
than once a calendar year). The Sublessor shall not in anyway be liable or
responsible to the Sublessee for any loss or damage or expense which the
Sublessee may sustain or incur if either the quantity or character of electric
service is changed or is no longer available or suitable for the Sublessee's
requirements.

     Section 3.03 The Sublessee hereby covenants and agrees to pay any and all
sums required to be paid by the Sublessee pursuant to the terms of this Sublease
to the Sublessor at the address set forth in Article 11, or at such other place
as the Sublessor may designate without notice or demand, abatement, deduction or
set-off of any amount whatsoever in lawful money of the

                                       3
<PAGE>

United States which shall be legal tender for the payment of all debts, public
and private at the time of payment.

     Section 3.04. On the date hereof the Sublessee shall deliver to the
Sublessor either (i) an irrevocable letter of credit in the amount of
$212,500.00, or (ii) a check, subject to collection, in the amount of
$212,500.00 (the "Security Deposit") as security for the Sublessee's performance
of the terms, covenants, conditions and provisions of this Sublease. The letter
of credit shall be issued by a bank and be in form and substance acceptable to
the Sublessor in its sole discretion. The. Sublessor shall have the right,
without notice to the Sublessee, to apply all or any portion of the Security
Deposit to cure any default by the Sublessee under this Sublease. In such event,
the Sublessee shall immediately deposit with the Sublessor an amount equal to
the portion of the Security Deposit so applied so that the Sublessor shall hold
the full amount of the Security Deposit at all times during the Term. The
Sublessee's failure to replenish the Security Deposit shall be an event of
default and any failure of a check delivered as a security deposit to clear
shall be an event of default. Any unapplied portion of the Security Deposit
shall be returned to the Sublessee within thirty (30) days after the expiration
of this Sublease provided that the Sublessee has complied with all of the terms,
covenants, conditions and provisions of this Sublease.

                     ARTICLE 4 Incorporation of Master Lease
                     ---------------------------------------

     Section 4.01. This Sublease is made upon the terms and conditions set forth
in, and is subject and subordinate to (i) the Master Lease and (ii) any
mortgages and ground leases which now or hereafter may be superior to the Master
Lease. A copy of the Master Lease has been delivered to the Sublessee and the
Sublessee hereby acknowledges that it has received, read and examined the Master
Lease and is fully familiar with all of its terms, covenants and provisions.

     Section 4.02. The Sublessor hereby warrants and represents that the Master
Lease is in full force and effect and that the Sublessor, subject to such
consents as are required under the Master Lease, is authorized and empowered to
enter into this Sublease.

     Section 4.03. Except as hereinafter provided in Section 4.05 of this
Sublease, the Sublessor and the Sublessee hereby agree that this Sublease shall
incorporate, and there is hereby incorporated into this Sublease, all of the
terms, covenants, conditions and provisions of the Master Lease with the same
force and effect as if such terms, covenants, conditions and provisions were set
forth herein in full as part of a direct lease from the Sublessor to the
Sublessee, and for the purposes of this incorporation, (a) the term "Tenant" in
the Master Lease means the Sublessee, (b)the term "Landlord" in the Master Lease
means the Sublessor, subject, however, to the limitations set forth in Section
4.05(e) and elsewhere in this Sublease, (c) the term "Demised Premises" in the
Master Lease means the Subleased Premises and (d) the term "Expiration Date" in
the Master Lease means the Sublease Expiration Date. In the event of any
inconsistency between the Master Lease and the specific provisions of this
Sublease, the specific provisions of this Sublease shall govern.

     Section 4.04. This Sublease is subject to, and the Sublessee hereby accepts
this Sublease subject and subordinate to, any amendments and supplements to the
Master Lease hereafter made between Prime Landlord and the Sublessor, provided
that any such amendment or supplement to

                                       4
<PAGE>

the Master Lease which would prevent or adversely affect the use by the
Sublessee of the Subleased Premises in accordance with the terms of this
Sublease, increase the obligations of the Sublessee, or decrease its rights
under this Sublease, shall not be deemed incorporated herein without the express
prior written consent of the Sublessee.

     Section 4.05 (a) For the purposes of this Sublease, the following
provisions of the Master Lease shall be deemed deleted and shall form no part of
this Sublease:

          Section 1.1(f), Section 1.1(g), Section 1.1(h), Section 1.1(j),
          Section 1.1(k), Section 1.1(1), Section 1. 1(u), Section 2. 1(a)
          (except for the last sentence thereof), Section 2.1(b), the last
          sentence of Section 3.2, the third sentence of Section 4.2(d), the
          first sentence of Section 4.9, the last sentence of Section 7.6(a),
          Section 7.7, Section 11.9, Section 11.10, Section 15.1(e), Article 21,
          Section 22.2, Article 25, Article 28, Article 43, Article 44, Exhibit
          B, and Exhibit F.

          (b) For the purposes of this Sublease, the following provisions of the
Master Lease are hereby amended as follows:

              (i)    Section 2.3(d) shall be deleted in its entirety and in lieu
thereof the following language shall be inserted: "Base Tax Year shall mean the
July 1, 1999 to June 30, 2000 Tax Year."

              (ii)   In Section 2.3(f), the words "2.3 percent (2.3%)" shall be
deleted and in lieu thereof the words "52/100 percent (.52%)" shall be inserted.

              (iii)  Section 2.3(h) shall be deleted in its entirety and in lieu
thereof the following language shall be inserted: "Base Wage Rate shall mean the
Wage Rate in effect for the calendar year 1999."

              (iv)   In the first sentence of Section 4.1(b), (a) the words
"Except with respect to Landlord's reimbursement for Tenant's Initial
Construction (as defined and set forth in Article 21 hereof)," shall be deleted
and (b) the next word "all" shall be capitalized.

              (v)    In the second sentence 01 Section 13.1, the words "Except
as expressly provided in Sections 3.2 and 4.2," shall be deleted.

              (vi)   In Section 26.4(a), the third sentence, the fifth sentence,
the sixth sentence and the seventh sentence shall be deleted.

              (vii)  In the first and second sentences of Section 40.1, the
phrase "twenty-five (25)" shall be deleted and in lieu thereof the phrase "six
(6)" shall be inserted.

              (viii) In the second sentence of Section 40.2, the phrase "twelve
(12)" shall be deleted and in lieu thereof the phrase "three (3)" shall be
inserted.

                                       5
<PAGE>

          (c) Wherever it is provided in the Master Lease that the Prime
Landlord has the right to elect to perform any covenant, term or provision
required to be complied with by the tenant thereunder upon default of such
tenant in observing or complying with such covenant, term or provision, such
right shall inure to the benefit of the Sublessor hereunder as well as to the
benefit of the Prime Landlord thereunder.

          (d) Nothing contained herein or in the Master Lease shall be construed
to require the Sublessor to cure any default of the Prime Landlord under the
Master Lease or to bring any action or proceeding or take any steps to enforce
the Sublessor's rights, if any, against the Prime Landlord in respect thereof.

          (e) Without limiting the generality of the foregoing provisions of
this Article 4 and notwithstanding anything in this Sublease or in the Master
Lease to the contrary, the parties hereto hereby agree that the Sublessor shall
not be responsible for furnishing any service or for doing any maintenance or
repairs to the Subleased Premises or for complying with any obligations required
of the Prime Landlord under the Master Lease, and the Sublessee in no event
whatsoever shall be entitled to any allowance, reduction or adjustment of the
Fixed Rent or additional rent payable under this Sublease by reason of the
failure of the Prime Landlord to comply with its obligations, if any, under the
Master Lease. The Sublessee shall look solely to the Prime Landlord for all
services, maintenance, repairs and the performance of all obligations required
to be performed by the Prime Landlord under the Master Lease and shall not under
any circumstances seek nor require the Sublessor to perform any such services,
maintenance, repairs or perform any of said obligations nor shall the Sublessee
make any claim upon the Sublessor for any damages which may arise by reason of
the Prime Landlord's default under the Master Lease or its negligence whether by
omission or commission. In furtherance of the foregoing, the Sublessee does, to
the extent permitted by law, waive any and all causes of action and any right to
bring an action against the Sublessor by reason of any act or omission of the
Prime Landlord under the Master Lease.

          (f) The Sublessee hereby agrees to perform and comply with all of the
terms, provisions, covenants and conditions of the Master Lease required to be
complied with by the tenant thereunder and not to do or suffer or permit
anything to be done which would result in default under or cause the Master
Lease to be terminated or forfeited. The Sublessee shall have no rights in the
Subleased Premises greater than the Sublessor's rights under the Master Lease.

                                ARTICLE 5 Notices
                                -----------------

     Section 5.01. Whenever in the Master Lease a time is specified for the
giving of any notice or the making of any demand by the tenant thereunder, such
time is hereby changed (for the purpose of this Sublease only) by adding two (2)
Business Days thereto, and whenever in the Master Lease a time is specified for
the giving of any notice or the making of any demand by the Prime Landlord
thereunder, such time is hereby changed (for the purpose

                                       6
<PAGE>

of this Sublease only) by subtracting two (2) Business Days therefrom. Whenever
in the Master Lease a time is specified within which the tenant thereunder must
give notice or make a demand following an event, or within which such tenant
must respond to any notice, request or demand previously given or made by the
Prime Landlord thereunder, such time is hereby changed (for the purpose of this
Sublease only) by subtracting two (2) Business Days therefrom. Whenever in the
Master Lease a time is specified within which the Prime Landlord thereunder must
give notice or make a demand following an event, or within which the Prime
Landlord must respond to any notice, request or demand previously given or made
by the tenant thereunder, such time is hereby changed (for the purpose of this
Sublease only) by adding two (2) Business Days thereto. It is the purpose and
intent of the foregoing provisions to provide the Sublessor with time within
which to transmit to the Prime Landlord any notices or demands received from the
Sublessee, and to transmit to the Sublessee any notices or demands received from
the Prime Landlord.

     Section 5.02. Notwithstanding anything contained in any provision of this
Sublease to the contrary, the Sublessee hereby agrees with respect to the
Subleased Premises to comply with and remedy any default under this Sublease
within the period allowed to the Sublessor as tenant under the Master Lease,
even if such time period is shorter than the period otherwise allowed therein
due to the fact that notice of default from the Sublessor to the Sublessee is
given after the corresponding notice of default from the Prime Landlord to the
Sublessor. The Sublessor hereby agrees to forward to the Sublessee, upon receipt
thereof by the Sublessor, a copy of all notices (including, without limitation,
notices of default), requests or demands which relate to the Subleased Premises,
or any portion thereof, received by the Sublessor in its capacity as tenant
under the Master Lease. The Sublessee hereby agrees to forward to the Sublessor,
upon receipt thereof, copies of any notices, requests or demands which relate to
the Subleased Premises, or any portion thereof, received by the Sublessee from
the Prime Landlord or from any governmental authorities.

            ARTICLE 6 Right of Sublessor to Cure Sublessee's Defaults
            ---------------------------------------------------------

     Section 6.01. If the Sublessee shall fail to perform any of the terms,
provisions, covenants or conditions of this Sublease on its part to be
performed, which failure constitutes a default under the Master Lease, then the
Sublessor may, at its option, perform any such term, provision, covenant or
condition, and the full cost and expense incurred shall immediately be due and
owing by the Sublessee to the Sublessor, together with interest thereon at the
Sublease Interest Rate from the date of payment thereof by the Sublessor.

     Section 6.02. If the Sublessee shall default in the performance or
observance of any term, covenant or agreement contained in this Sublease, or in
the Master Lease, as herein incorporated, or breach any representation or
warranty herein, then, in any one or more of such events, if such default shall
not have been remedied after notice given by the Sublessor to the Sublessee and
within the grace period, if any (as such period is modified by the provisions of
Article 5 of this Sublease), provided for under the Master Lease, the Sublessor
shall be entitled to exercise any and all rights and remedies to which the
Sublessor is entitled by law and equity or as are specifically granted to the
Prime Landlord under the Master Lease, which rights and remedies are hereby
incorporated herein and made a part hereof with the same force and effect as
though herein specifically set forth, and the Sublessee shall remain liable as
provided for in the Master Lease.

     Section 6.03. The Sublessee hereby agrees to indemnify the Sublessor and
hold the Sublessor harmless from and against any and all loss, liability,
damage, penalty, cost, claim,

                                       7
<PAGE>

demand, judgment, charge and expense of every kind whatsoever, including
reasonable attorneys' fees, arising out of or incurred in connection with any:

          (a) failure of or by any Sublessee of the Sublessee's interests
hereunder to perform or comply with any and all of the terms, covenants,
conditions and provisions of this Sublease and the Master Lease or breach of any
representation and warranty contained herein;

          (b) use or occupancy by the Sublessee of the Subleased Premises or
from any work of any kind done or omitted to be done, in, on, or about the
Subleased Premises or the Building by the Sublessee or the Sublessee's
employees, contractors, agents, or licensees (including, but not limited to,
construction, alterations, repairs, or similar acts of any kind whatsoever, and
whether or not authorized by this Sublease);

          (c) negligence or willful act or omission of the Sublessee or its
employees, contractors, agents or licensees;

          (d) injuries to persons or property occurring in, on or about the
Subleased Premises or the Building caused by the Sublessee or Sublessee's
employees, contractors, agents, or licensees; and

          (e) any action or proceeding brought against Sublessor by reason of
this Sublease and arising out of any of the circumstances enumerated in
subsections (a) through (d) of this Section 6.03.

     If any action, suit or proceeding shall be brought against the Sublessor in
connection with any matter covered by the indemnity set forth in this Section
6.03, the Sublessee, at the election of the Sublessor and on notice from the
Sublessor, shall defend such action, suit or proceeding at the Sublessee's
expense with counsel approved by the Sublessor.

                  ARTICLE 7 Consents and Approvals of Sublessor
                  ---------------------------------------------

     Section 7.01. The Sublessee hereby agrees that in any case where the
provisions of this Sublease require the consent or approval of the Sublessor
prior to the taking of any action, it shall be a condition precedent to the
taking of such action that the prior written consent or approval of the Prime
Landlord shall have been obtained if the consent of the Prime Landlord must be
obtained under the Master Lease in such cases. The Sublessee hereby agrees that
the Sublessor shall not have any duty or responsibility with respect to
obtaining the consent or approval of the Prime Landlord when the same is
required under the terms of the Master Lease, other than the mere transmission
by the Sublessor to the Prime Landlord of the Sublessee's request for such
consent or approval. If the Prime Landlord shall delay any such consent or
approval, the Sublessor may similarly delay any consent or approval to the
Sublessee. If the Prime Landlord shall refuse such consent or approval, the
Sublessor shall be released from any obligation to grant its consent or
approval, whether or not the Prime Landlord's refusal, in the Sublessee's
opinion, is arbitrary or unreasonable.

                                       8
<PAGE>

                               ARTICLE 8 Brokerage
                               -------------------

     Section 8.01. The Sublessor hereby represents and warrants to the Sublessee
that it has dealt with no brokers, agents or finders other than Studley in
connection with the execution of this Sublease or the transactions contemplated
by this Sublease. The Sublessor agrees to pay the commission due and payable to
Studley pursuant to a separate written agreement between the Sublessor and
Studley.

     Section 8.02. The Sublessee hereby represents and warrants to the Sublessor
that it has dealt with no brokers, agents or finders other than PMR in
connection with the execution of this Sublease or the transactions contemplated
by this Sublease.

     Section 8.03. The Sublessor hereby agrees to indemnify and hold the
Sublessee harmless from and against any commission or fee claim by any person
with whom the Sublessor has dealt with other than Studley and PMR in connection
with the negotiation and execution of this Sublease or any matter whatsoever
pertaining or related thereto. This indemnification shall also cover any and all
expenses which the Sublessee incurs to defend against any such commission or fee
claim including, but not limited to, reasonable attorneys' fees.

     Section 8.04. The Sublessee hereby agrees to indemnify and hold the
Sublessor harmless from and against any commission or fee claim by any person
with whom the Sublessee has dealt with other than Studley in connection with the
negotiation and execution of this Sublease or any matter whatsoever pertaining
or related thereto. This indemnification shall also cover any and all expenses
which the Sublessor incurs to defend against any such commission or fee claim
including, but not limited to, reasonable attorneys' fees.

     Section 8.05. The representations, warranties and indemnifications set
forth in this Article 8 shall survive the expiration or sooner termination of
this Sublease.

                       ARTICLE 9 Consent of Prime Landlord
                       -----------------------------------

     Section 9.01. Notwithstanding anything in this Sublease to the contrary,
the parties hereto hereby expressly acknowledge and agree that this Sublease is
conditioned upon the Sublessor' s obtaining such consents hereto as are required
by the provisions of the Master Lease. Promptly following the execution by the
Sublessee and the Sublessor of this Sublease, the Sublessor hereby agrees to use
commercially reasonable efforts to obtain such consents. The Sublessee hereby
agrees to cooperate in obtaining such consents. The Sublessor shall promptly
notify the Sublessee when such consents have been obtained. If the consent of
the Prime Landlord, or any other consent required by the Master Lease as a
condition to the Sublessor's entering into this Sublease, is not obtained within
sixty (60) days after the execution hereof, either party hereto may cancel this
Sublease at any time prior to the obtaining of said consent(s) by giving written
notice to the other. Upon such cancellation neither party hereto shall have any
further rights or obligations hereunder except such rights and obligations which
expressly survive the termination of this Sublease.

                                       9
<PAGE>

                 ARTICLE 10 Insurance; Alterations; Restoration
                 ----------------------------------------------

     Section 10.01. At its sole cost and expense the Sublessee will obtain and
maintain any and all liability and casualty insurance of any kind whatsoever
with respect to the Subleased Premises which the Sublessor is required to
maintain as tenant under the Master Lease. If the Sublessee fails to maintain
any such insurance, the Sublessor may, at its election, obtain the same and
collect the cost thereof from the Sublessee as additional rent, upon demand,
with interest thereon at the Sublease Interest Rate from the date of such
demand.

     Section 10.02. The Sublessee shall make no alterations, improvements,
decorations, or installations of any kind whatsoever, in or to the Subleased
Premises without the prior written consent of the Sublessor and without the
prior written consent of the Prime Landlord. The Sublessee hereby agrees that
the Sublessee's employment of any contractor, subcontractor, or other person in
connection with the alteration, restoration, improvement or decoration of the
Subleased Premises (or any portion thereof) shall be expressly subject to the
approval of the Prime Landlord and the Sublessor.

     Section 10.03. The Sublessee shall restore the Subleased Premises at the
end of the Term and surrender the same to the Sublessor in the same condition
which existed on the date hereof, reasonable wear and tear excepted.

                               ARTICLE 11 Notices
                               ------------------

     Section 11.01. All notices, requests, demands, elections, consents,
approvals and other communications required or permitted to be given hereunder
shall be in writing (each such, a "notice") and addressed as follows (or to such
other address as either party may by previous written notice have designated):

     If to the Sublessor:
     -------------------

          Dover Corporation
          280 Park Avenue
          New York, New York 10017
          Attention:  Robert G. Kuhbach, Esq.

     with a copy to:

          Coudert Brothers
          1114 Avenue of the Americas
          New York, New York 10036
          Attention:  Gerard V. Hannon, Esq.

                                       10
<PAGE>

     If to the Sublessee:
     -------------------

          OneSoft Corporation
          7010 Little River Turnpike, Suite 460
          Annandale, VA 22003
          Attention:  Paul Economon, Esq.

Any notice under this Sublease shall be deemed to have been given only if
delivered by hand (with receipt), sent by Federal Express (with receipt) or
mailed by first class registered or certified mail (return receipt requested),
postage and fees prepaid.  Each notice delivered by hand shall be deemed given
on the day received or rejected, and each notice delivered by mailing or Federal
Express shall be deemed given three (3) Business Days after mailing or delivery
to said courier.

                            ARTICLE 12 Miscellaneous
                            ------------------------

     Section 12.01. This Sublease shall be governed by and construed in
accordance with the laws of the State of New York, without regard to conflicts
of law provisions.

     Section 12.02. The table of contents and the headings of the various
subdivisions of this Sublease are used for reference only and are not to be
taken as part of this Sublease, or to be used in determining the intent of the
parties, or otherwise affect the meaning of this Sublease. All pronouns shall be
deemed to refer to the masculine, feminine, neuter, singular or plural as the
identity of the person or persons may require.

     Section 12.03. This Sublease shall be binding upon and inure to the benefit
of the parties hereto and their respective heirs, distributees, executors,
administrators, successors and permitted assigns. This Section shall not be
construed as a consent to any assignment or subletting by the Sublessee.

     Section 12.04. No covenant, agreement, term or condition of this Sublease
to be performed or complied with by the Sublessee, and no breach thereof, shall
be waived, altered or modified except by a written instrument executed by the
Sublessor. No waiver of any breach shall affect or alter this Sublease, but each
and every term, covenant, condition and provision of this Sublease shall
continue in full force and effect with respect to any other then existing or
subsequent breach.

     Section 12.05. No agreement to accept any surrender of the Subleased
Premises shall be valid unless in writing and duly executed by the Sublessor and
the Sublessee. Except pursuant to a written agreement duly executed by the
Sublessee and the Sublessor, no act or thing done by the Sublessor or its agents
during the Term shall be deemed an acceptance of a surrender of the Subleased
Premises. No agent or employee of the Sublessor shall have any power to accept
the keys of the Subleased Premises prior to the termination of this Sublease and
delivery of keys to any such agent or employee shall not operate as a
termination of this Sublease or a surrender of the Subleased Premises.

                                       11
<PAGE>

     Section 12.06. This Sublease embodies the entire agreement and
understanding between the parties hereto and supersedes all prior agreements and
understandings relating to the subject matter hereof. This Sublease may not be
modified or amended or any term or provision hereof waived or discharged except
in writing and signed by the party against whom such amendment, -modification,
waiver or discharge is sought to be enforced.

     Section 12.07. This Sublease may be executed in several counterparts, each
of which shall be deemed an original but all of which together shall constitute
one and the same instrument.

     Section 12.08. If any term or provision of this Sublease or the application
thereof to any person or circumstances shall, to any extent, be invalid or
unenforceable, the remainder of this Sublease or the application of such term or
provision to persons or circumstances other than those as to which it is held
invalid or unenforceable shall remain valid and enforceable to the extent
permitted by law.

     Section 12.09. The Sublessee shall from time to time, upon the request of
the Sublessor, execute, deliver and furnish such documents as the Sublessor may
reasonably deem necessary or desirable to (a) correct any errors which may be
contained in this Sublease and (b) fully consummate the transactions
contemplated under this Sublease.

     Section 12.10. The parties hereto do not intend to confer any benefit
hereunder on any person, firm or corporation other than the parties hereto.

     Section 12.11. Time shall be of the essence with respect to the Sublessee's
obligations contained in this Sublease.

     Section 12.12. This Sublease shall not be binding or effective until
properly executed and delivered by the parties hereto.

                                       12
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have caused this Sublease to be duly
executed by their authorized signatories on the day and year first hereinabove
written.

                                        SUBLESSOR

                                        DOVER CORPORATION


                                        By:  /s/ Robert G. Kuhback
                                           -------------------------------------
                                           Name:  Robert G. Kuhback
                                           Title:  Vice President


                                        SUBLESSEE

                                        ONESOFT CORPORATION

                                        By:  /s/ Frederick C. Hawkins, III
                                           -------------------------------------
                                           Name:  Frederick C. Hawkins, III
                                           Title:  Chief Financial Officer

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                                    Exhibit A

                               Floor Plan Attached

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