Document:

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                                                                   EXHIBIT 10.12
                                                                   -------------

                          [FORM OF] STANDARD SUBLEASE

     1.   Parties. This Sublease, dated, for reference purposes only, July 31,
2000, is made by and between GUY F. ATKINSON CONSTRUCTION CORPORATION (as
assignee of Guy F. Atkinson Company) (Sublessor") and VERISITY DESIGN, INC.
("Sublessee").

     2.   Premises. Sublessor hereby subleases to Sublessee and Sublessee hereby
subleases from Sublessor for the term, at the rental, and upon all of the
conditions set forth herein, those certain office premises in the Building
located at 110 TURNPIKE ROAD, WESTBOROUGH located in the County of WORCESTER
State of MASSACHUSSETTS and generally described as (describe briefly the nature
of the property) 3,638 rentable square feet on the first floor of such Building
("Premises").

     3.   Term.

     3.1  Term. The term of this Sublease shall be for NINETEEN (19) MONTHS
commencing on AUGUST 1, 2000 and ending on FEBRUARY 28, 2002 unless sooner
terminated pursuant to any provision hereof. Notwithstanding the foregoing, the
term of this Sublease shall not commence prior to the date that Sublessor has
obtained the consent of the Master Lessor hereto pursuant to Paragraph 9.1 of
this Sublease. Sublessor shall not deliver possession of the Premises to
Sublessee until such consent has been obtained.

     3.2  Delay in Commencement. Sublessor agrees to use its best commercially
reasonable efforts to deliver possession of the Premises by the commencement
date. If, despite said efforts, Sublessor is unable to deliver possession as
agreed on or before August 15, 2000, Sublessee shall have the right to terminate
this Sublease upon written notice to Sublessor, whereupon Sublessor shall return
to Sublessee within five (5) days thereafter all prepaid rent and security
deposit.

     4.   Rent.

     4.1  Base Rent. Sublessee shall pay to Sublessor as Base Rent for the
Premises equal monthly payments of $6,670 in advance, on the FIRST day of each
month of the term hereof, provided that Sublessee shall pay Sublessor upon the
execution hereof $8,338 as Base Rent for the first two (2) months of the term of
this Sublease. The parties acknowledge that the operating expenses under the
Master Lease are included in the Base Rent under this Sublease. Base Rent for
any period during the term hereof which is for less than one month shall be a
pro rata portion of the monthly installment.

     4.2  Rent Defined. All monetary obligations of Sublessee to Sublessor under
the terms of this Sublease (except for the Security Deposit) are deemed to be
rent ("Rent"). Rent shall be payable in lawful money of the United States to
Sublessor at the address stated herein or to such other persons or at such other
places as Sublessor may designate in writing.

     5.   Security Deposit. Sublessee shall deposit with Sublessor upon delivery
of the Premises and receipt of Master Lessor's consent, $40,020 in accordance
with Paragraph 12.2 hereof as security for Sublessee's faithful performance of
Sublessee's obligations hereunder. The rights and obligations of Sublessor and
Sublessee as to said Security Deposit shall be as set forth in the Master Lease
(as modified by Paragraph 7.3 of this Sublease).

     6.   Use.

     6.1  Agreed Use. The Premises shall be used and occupied only for general
office use and for no other purpose.

     6.2  Compliance. Sublessor warrants that the improvements on the Premises
comply with all applicable covenants or restrictions of record and applicable
building codes, regulations and ordinances ("Applicable Requirements") in effect
on the commencement date. Said warranty does not apply to the use to which
Sublessee will put the Premises or to any alterations or utility installations
made or to be made by Sublessee. NOTE: Sublessee is responsible for determining
whether or not the zoning is appropriate for its intended use, and acknowledges
that past uses of the Premises may no longer be allowed.

     6.3  Acceptance of Promises and Lessee. Sublessee acknowledges that:

     (a)  it has been advised by Brokers to satisfy itself with respect to the
condition of the Premises (including but not limited to the electrical, HVAC and
fire sprinkler systems, security, environmental aspects, and compliance with
Applicable Requirements), and their suitability for Sublessee's intended use,

     (b)  Sublessee has made such investigation as it deems necessary with
reference to such matters and assumes all responsibility therefor as the same
relate to its occupancy of the Premises, except to the extent that the same is
the obligation of the Master Lessor under the Master Lease, and

     (c)  Neither Sublessor, Sublessor's agents, nor any Broke has made any oral
or written representations or warranties with respect to said matters other than
as set forth In this Sublease.

In addition, Sublessor acknowledges that:

     (a)  Broker has made no representations, promises or warranties concerning
Sublessee's ability to honor the Sublease or suitability to occupy the Premises,
and
     (b)  it is Sublessor's sole responsibility to investigate the financial
capability and/or suitability of all proposed tenants.

                                       1
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     7.   Master Lease

     7.1  Sublessor is the lessee of the Premises by virtue of a lease,
hereinafter the "Master Lease", a copy of which is attached hereto marked
Exhibit 1, wherein OTR, an Ohio general partnership (as succcessor to
WESTBOROUGH EXECUTIVE PARK LLC) is the lessor, hereinafter the "Master Lessor".

     7.2  This Sublease is and shall be at all times subject and subordinate to
the Master Lease.

     7.3  The terms, conditions and respective obligations of Sublessor and
Sublessee to each other under this Sublease shall be the terms and conditions of
the Master Lease except for those provisions of the Master Lease which are
directly contradicted by this Sublease in which event the terms of this Sublease
document shall control over the Master Lease. Therefore, for the purposes of
this Sublease, wherever in the Master Lease the word "Lessor" is used it shall
be deemed to mean the Sublessor herein and wherever in the Master Lease the word
"Lessee" is used it shall be deemed to mean the Sublessee herein.
Notwithstanding anything to the contrary contained in this Sublease, Section 4
of the Master Lease shall be excluded from this Sublease, the parties
acknowledging that Sublessee shall not be required to pay Operating Expenses
under the Master Lease.

     7.4  During the term of this Sublease and for all periods subsequent for
obligations which have arisen during the term of this Sublease, Sublessee does
hereby expressly assume and agree to perform and comply with, for the benefit of
Sublessor and Master Lessor, each and every obligation of Sublessor under the
Master Lease.

     7.5  The obligations that Sublessee has assumed under paragraph 7.4 hereof
are hereinafter referred to as the "Sublessee's Assumed Obligations". The
obligations that Sublessee has not assumed under paragraph 7.4 hereof are
hereinafter referred to as the "Sublessor's Remaining Obligations".

     7.6  Sublessee shall hold Sublessor free and harmless from all liability,
judgments, costs, damages, claims or demands, including reasonable attorneys'
fees, arising out of Sublessee's failure to comply with or perform Sublessee's
Assumed Obligations.

     7.7  Sublessor represents to Sublessee that the Master Lease is in full
force and effect and that no default exists on the part of any Party to the
Master Lease, and that the Master Lease has not been amended in any way except
as shown on Exhibit 1. Sublessor represents that the current term of the Lease
will expire on February 28, 2002.

     8.   Assignment of Sublease and Default.

     8.1  Sublessor hereby assigns and transfers to Master Lessor the
Sublessor's interest in this Sublease, subject however to the provisions of
Paragraph 8.2 hereof.

     8.2  Master Lessor, by executing this document, agrees that until Default
shall occur in the performance of Sublessor's Obligations under the Master
Lease, that Sublessor may receive, collect and enjoy the Rent accruing under
this Sublease. However, if Sublessor shall Default in the performance of its
obligations to Master Lessor then Master Lessor may, at its option, receive and
collect, directly from Sublessee, all Rent owing and to be owed under this
Sublease. Master Lessor shall not, by reason of this assignment of the Sublease
nor by reason of the collection of the Rent from the Sublessee, be deemed liable
to Sublessee for any failure of the Sublessor to perform and comply with
Sublessor's Remaining Obligations.

     8.3  Sublessor hereby irrevocably authorizes and directs Sublessee upon
receipt of any written notice from the Master Lessor stating that a Default
exists in the performance of Sublessor's obligations under the Master Lease, to
pay to Master Lessor the Rent due and to become due under the Sublease.
Sublessor agrees that Sublessee shall have the right to rely upon any such
statement and request from Master Lessor, and that Sublessee shall pay such Rent
to Master Lessor without any obligation or right to inquire as to whether such
Default exists and notwithstanding any notice from or claim from Sublessor to
the contrary and Sublessor shall have no right or claim against Sublessee for
any such Rent so paid by Sublessee.

     8.4  No changes or modifications shall be made to this Sublease without the
consent of Master Lessor.

     9.   Consent of Master Lessor.

     9.1  In the event that the Master Lease requires that Sublessor obtain the
consent of Master Lessor to any subletting by Sublessor then, this Sublease
shall not be effective unless, within ten days of the date hereof, Master Lessor
signs this Sublease or otherwise gives its consent to this Subletting in a form
reasonably acceptable to Sublessee, which consent shall include an
acknowledgement that the current condition of the Premises satisfies the
requirements under the Master Lease for delivery of the Premises back to Master
Lessor upon termination of the Master Lease and that Master Lessor will not
require that any currently-existing alterations to the Premises be removed upon
the expiration of the Master Lease.

     9.2  In the event that the obligations of the Sublessor under the Master
Lease have been guaranteed by third parties then neither this Sublease, nor the
Master Lessor's consent, shall be effective unless, within 10 days of the date
hereof, said guarantors sign this Sublease thereby giving their consent to this
Sublease.

     9.3  In the event that Master Lessor does give such consent then:

     (a)  Such consent shall not release Sublessor of its obligations or alter
the primary liability of Sublessor to pay the Rent and perform and comply with
all of the obligations of Sublessor to be performed under the Master Lease.

     (b)  The acceptance of Rent by Master Lessor from Sublessee or anyone else
liable under the Master Lease shall not be deemed a waiver by Master Lessor of
any provisions of the Master Lease.

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     (c)  The consent to this Sublease shall not constitute consent to any
subsequent subletting or assignment.

     (d)  Master Lessor may consent to subsequent subletting and assignments of
the Master Lease or this Sublease or any amendments or modifications thereto
without notifying Sublessor or any one else liable under the Master Lease and
without obtaining their consent and such action shall not relieve such persons
from liability.

     (e)  In the event that Sublessor shall Default in its obligations under the
Master Lease, then Master Lessor, at its option and without being obligated to
do so, may require Sublessee to attorn to Master Lessor in which event Master
Lessor shall undertake the obligations of Sublessor under this Sublease from the
time of the exercise of said option to termination of this Sublease but Master
Lessor shall not be liable for any prepaid Rent nor any Security Deposit paid by
Sublessee, nor shall Master Lessor be liable for any other Defaults of the
Sublessor under the Sublease.

     9.4  The signatures of the Master Lessor and any Guarantors of Sublessor at
the end of this document shall constitute their consent to the terms of this
Sublease.

     9.5  Master Lessor acknowledges that, to the best of Master Lessors
knowledge, no Default presently exists under the Master Lease of obligations to
be performed by Sublessor and that the Master Lease is in full force and effect.

     9.6  In the event that Sublessor Defaults under its obligations to be
performed under the Master Lease by Sublessor, Master Lessor agrees to deliver
to Sublessee a copy of any such notice of default. Sublessee shall have the
right to cure any Default of Sublessor described in any notice of default within
ten days after service of such notice of default on Sublessee. If such Default
is cured by Sublessee then Sublessee shall have the right of reimbursement and
offset from and against Sublessor.

     10.  Brokers Fee.

     10.1 Upon execution hereof by all parties, Sublessor shall pay to CB
RICHARD ELLIS/WHITTIER PARTNERS a licensed real estate broker, ("Broker"), a fee
as set forth in a separate agreement between Sublessor and Broker for brokerage
services rendered by Broker to Sublessor in this transaction.

     11.  Attorney's Fees. If any party or the Broker named herein brings an
action to enforce the terms hereof or to declare rights hereunder, the
prevailing party in any such action, on trial and appeal, shall be entitled to
his reasonable attorney's fees to be paid by the losing party as fixed by the
Court.

     12.  Additional Provisions.

     12.1 Sublessee shall maintain insurance requirements per the Master Lease.
          A certificate of insurance, in a form acceptable to Sublessor, must be
          received by Sublessor prior to occupancy of the Premises by Sublessee.

     12.2 The Security Deposit shall conform to the following terms:

          (i)   A cash security deposit equal to two (2) months of rent or
                $13,340 to be held by Sublessor for the full term of this
                Sublease.

          (ii)  Upon Master Lessor's consent and prior to occupancy, a letter of
                credit, in a form reasonably acceptable to Sublessor, equal to
                an additional four (4) months of rent or $26,680. Provided that
                Sublessee is not in default of any of the provisions of this
                Sublease for the first nine (9) months of the Term, the
                Sublessor shall return said letter of credit to the Sublessee
                within 10 days of the end of the ninth (9/th/) month.

     12.3 Rent shall be sent to the following address:
          Attn: A/P-A/R MANAGER
          Guy F. Atkinson Construction Corporation
          C/o The Clark Construction Group, Inc.
          7500 Old Georgetown Road, Suite 300
          Bethesda, Maryland 20814

     12.4 Sublessor shall bill Sublessee $0.80 per rentable square foot (+/-
          3,638sf) per year for electricity.

     12.5 Sublessee shall have no liability for the failure of Sublessor to
perform any of its obligations under the Master Lease occurring prior to the
commencement of the term of this Sublease.

                                       3
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     12.6 By executing this Sublease below, Master Lessor consents to the
subletting and acknowledges that the current term of the Master Lease expires on
February 28, 2002.

on:___________________________________    By:___________________________________
                                             GUY F. ATKINSON CONSTRUCTION
                                             CORPORATION,
                                             "Sublessor" (Corporate Seal)

on:____________________________________   By:___________________________________
Address:_______________________________      VERISITY DESIGN, INC.
                                             "Sublessee" (Corporate Seal)

on:____________________________________   By:___________________________________
Address:_______________________________   By:___________________________________
                                             "Master Lessor" (Corporate Seal)

                                       4<PAGE>

                                                                   EXHIBIT 10.13
                                                                   -------------

VANTAS

                           OFFICE SERVICES AGREEMENT

This Agreement is made August 6, 1999, by and between Austin Mopac d/b/a/ VANTAS
("Center") having offices known and numbered as Suite A101 (the "Facility") in
the building located at 8303 North Mopac Expressway, Austin, TX 78759
(the "Building") and Verisity Design ("Client") a(n) (corporation, partnership,
individual) with an address of 2041 Landings Drive, Mountain View, CA 94043 for
a term of 12 months, commencing on October 1, 1999 (the "Commencement Date") and
ending on September 30, 2000 (the "Initial Term") unless renewed in accordance
with Paragraph 3.

     In consideration of the foregoing, the parties for themselves, their heirs,
legal representatives, successors and assigns, agree as follows:

     1.   Center's Obligations.

     a.   Subject to the terms and conditions of this Agreement, Center hereby
agrees to provide Client for the Term (as defined below in Paragraph 3): (a) the
exclusive use of Furnished Private Office(s) number(s) 159, 160, 173 located
in the Facility (the "Premises"); and (b) non-exclusive use of the following
services:

 .    Furnished, Decorated Reception Room with Professional Receptionist

 .    Personalized Telephone Answering During Office Hours

 .    24 hour Voicemail

 .    24 hours of Conference Room per month subject to prior scheduling and use
     --
     by other Clients

 .    Corporate Identity on Lobby Directory where Available

 .    Receipt of Mail and Packages

 .    Complete Kitchen Facilities with Coffee Service

 .    Utilities and Maintenance

 .    HVAC During Normal Business Hours

 .    Janitorial Services

 .    8 hours per month courtesy use of other VANTAS affiliated facilities.
     Locations subject to current affiliation and availability.

     b.   If, for any reason, Center cannot deliver possession of the Premises
to Client on the Commencement Date, this Agreement will remain in full force and
effect; however, there will be an abatement of the Monthly Office Charge for the
period between the Commencement Date and the date that the Premises are
delivered to Client.

     2.   Use.
          ---

     The Premises will be used by Client solely for business purposes and such
                                                    -----------------
     other normally incident uses and for no other purpose, in strict accordance
     with the Operation Standards, which are annexed hereto as Schedule A.
     Client will not offer at the Premises any services which Center provides to
     its Clients, including, but not limited to those services described in
     Paragraph 1.  Client will not make nor permit to be made any use of the
     Premises, Facility or Building which would violate any of the terms of this
     Agreement or which, directly or indirectly, is forbidden by law, rule or
     regulation, which may be dangerous to life, limb or property or which could
     in any way impair, interfere or tend to impair or interfere with the high
     quality character, reputation or appearance of the Building or the Facility
     or with any services performed by Center for Client or for others.  The
     foregoing provisions will also apply to Client's Users (as defined in
     Paragraph 9).

3.   Renewal.
     -------

     Upon expiration of the Initial Term and on any subsequent renewal term
(each, a "Renewal Term" and together with the Initial Term, the "Term") of this
Agreement, the Agreement automatically will be extended for the same period of
time as the Initial Term and upon the same terms and conditions as herein
contained except for the amount of the Monthly Office Charge (as defined in
Paragraph 4) then in effect, which will each be negotiated between the parties
                                             ---------------------------------
and increased by no more than seven percent (7%), unless either party notifies
---              ------------
the other in writing within the period hereinafter specified that the Agreement
will not be extended.  If Client has less than three offices, such notice will
be given at least sixty (60) days prior to the expiration of the Initial Term or
the Renewal Term, as the case may be.  If Client has three or more offices, such
notice will be given at least ninety (90) days prior to the expiration of the
Initial Term or the Renewal Term, as the case may be.

     4.   Monthly Office Charge.
          ---------------------

     a.   For and during the Term of this Agreement, Client will pay to Center,
on or before the first day of each month after the Commencement Date, the sum of
$3,220.00 as Monthly Office Charge (subject to increase in accordance with
Paragraph 3 above) for the Premises.  If any payment of Monthly Office Charge or
other charge due under this Agreement is not received within five (5) calendar
days after its due date, the Client will also pay, in addition to Monthly Office
Charge, a late payment charge which will be an amount equal to ten percent (10%)
of any amount owed to Center or fifty dollars ($50.00) whichever is greater.
The financial terms of this Agreement are strictly confidential and Client
agrees not to knowingly or willfully divulge this information to any other
Client or potential Client of Center.

     b.   The Monthly Office Charge payable during the Term of this Agreement is
subject to increase following notification of any increase in the rent,
operating expenses or taxes which the Center might receive under the Main Lease
(as defined in Paragraph 20), including any increase in respect of past periods
under the Term.

                                       1
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Center will promptly notify Client in writing of any such increase, and will
bill Client for its pro rata share thereof.

     c.   The Monthly Office Charge is based on the value of the use of the
Premises and services to be used by 2 person(s) only.  If more than said number
                                    -
of person(s) regularly use the Premises or services, the Monthly Office Charge
will be increased in an amount equal to $0.00 for each such additional person.

     d.   If a Client check is returned for any reason, Client will pay an
additional charge of One Hundred Dollars ($100.00) per returned check and, for
the purpose of considering default and/or late charges, it will be as if the
payment represented by the returned check had never been made.

     5.   Refundable Retainer.
          -------------------

     a.   Client will deposit with Center $3,170.00, in good or certified
funds, as a non-interest bearing refundable retainer. Center may use the
refundable retainer to cure any default of Client under this Agreement, to
restore the Premises, including any and all furniture, fixtures and equipment,
provided by Center to its original condition and configuration, reasonable wear
and tear excepted, to pay for repairs to any damage to the Premises, Facility
and/or Building, caused by Client or Client's guests, or to pay any Monthly
Office Charge or other charges that Client owes Center at or prior to the
expiration of the Term of this Agreement.

     b.   The refundable retainer (less any sums used by Center in accordance
with the terms and conditions of this Agreement) will be returned within sixty
(60) days after the termination of any services rendered or expiration of the
Term. Client may not direct or request that the refundable retainer be applied
in lieu of the final payment(s) of Monthly Office Charge or service charges
under this Agreement.

     c.   In the event that Center applies any of the refundable retainer
deposited pursuant to this Agreement, Center will have the right to charge the
Client, and Client will pay, in addition to any Monthly Office Charge, such sums
as are necessary to cause the refundable retainer to be returned to its entire
original amount.

     6.   Services.
          --------

     a.   Provided Client is not in default of this Agreement, Center will make
available certain services to Client as more particularly described in Paragraph
1.  Charges for such services will be included as part of the Monthly Office
Charge.

     b.   Client shall pay a monthly amount equal to $120.00 per office in
respect of the monthly service package (the "Monthly Service Package"). Payment
of such amount will be on the same terms and conditions as those governing the
payment of the Monthly Office Charge. The Monthly Service Package will entitle
the Client to receive upon request and aggregate of four hours per month of
clerical and/or word processing services from the center.

     c.   In addition to the Monthly Service Package, upon request, Center will
make available to Client additional services as Center may make generally
available, the charges for which will be established as per Center's then
scheduled rates as determined by Center.  Payment for these services will be
subject to the same terms and conditions as those governing the payment of the
Monthly Office Charge.  Center will have no obligation to provide such services
if Client is in default of this Agreement or if the anticipated charges exceed
the amount of the refundable retainer.  When providing services to Client that
involve third parties, Center will have the right to require Client to pay, or
to reimburse Center for, the fees and expenses of such third party in advance.

     7.   Telephone Service.
          -----------------

     a.   Provided Client is not in default of this Agreement, Center will make
available to Client a telecommunications package, the charges for which will be
established as per Center's then scheduled rates as determined by Center.
Payment for these services will be subject to the same terms and conditions as
those governing the payment of the Monthly Office Charge.  All telephone numbers
used by Client will remain at all times the property of Center and Client will
acquire no rights in the components of the telecommunications package
whatsoever.

     b.   Client hereby agrees to indemnify, hold harmless and to reimburse
Center for all charges associated with (1) any toll fraud traceable to
telecommunications services provided by Center to Client including, but not
limited to, unauthorized use of calling cards or telephone lines, and (2) any
advertising costs of Client involving the telephone number assigned to it,
including, without limitation, yellow pages advertising (it being understood
that Center is under no obligation to procure such advertising and that any such
advertising by Client is subject to the Operations Standards).

     c.   It is expressly acknowledged and agreed that Center will be the sole
and exclusive provider of telecommunication services to Client. Client hereby
agrees and covenants that it will not use any other telephone service or
telephone carrier to provide it service in the Premises.

     d.   Center shall not be liable for any interruption or error in the
performance of its services to Client under this Paragraph "7."  Client waives
any recourse against Center arising from the provision of such services,
including, without limitation, any claim of business interruption or for any
indirect, incidental, special, consequential or punitive damages, except for
claims arising out of willful misconduct by Center.

     8.   Indemnity/Limitation of Liability/Insurance.
          -------------------------------------------

     a.   Client will indemnify and hold harmless Center from and against any
loss, damage, injury, liability or expense to or of person or property
occasioned by or resulting from any willful misconduct or grossly negligent act
on the part of Client or Client's Users. Center will not be liable to Client or
to any other person on account of loss, damage or theft to any business or
personal property of Client. Center will not be liable for any loss, damage,
injury, liability or expense to or of person or property except as may result
from Center's willful misconduct or grossly negligent acts. Center will
indemnify and hold harmless Client from and against any loss, damage, injury,
liability or expense to or of person or property occasioned by or resulting from
any willful misconduct or grossly negligent act on the part of the Center, its
agents, employees, or invitees, or persons permitted on the Premises by Center.

     b.   Center will not be liable for any claim of business interruption or
for any indirect, incidental, special, consequential exemplary or punitive
damages arising out of any failure to furnish any service or facility, any error
or omission with respect thereto, or any delay or interruption of same. Neither
Center nor any of its agents, employees, officers or directors will be deemed to
be making any representations or warranties, whether express or implied, as to
the ability of any systems, including, without limitation, computer and
electronic based equipment, relating to the Building, Facility or Premises or to
any services to be provided hereunder to process data fields relating to the
Year 2000 nor will any of them be liable for the failure of such systems to
process such data fields. Center's liability under this Agreement will in no
event exceed the amount paid by Client for the services for which the claim
arose. The parties agree to the allocation of risk contained herein.

                            [Subsection c deleted.]

                                       2
<PAGE>

     d.   The provisions of this Paragraph 8 will survive the expiration or
earlier termination of the term of this Agreement.

     9.   Operating Standards.
          -------------------

     The Operating Standards attached to this Agreement as Schedule A are hereby
made an integral part of this Agreement.  Client, its employees, agents, guests,
invitees, visitors and/or any other persons caused to be present in and around
the Premises by the Client ("Client's Users") will perform and abide by the
Operating Standards then in effect.

     10.  Employment of Center's Employees.
          --------------------------------

     Client agrees that it will not, during the Term of this Agreement and for a
period of one year thereafter, directly or indirectly, employ or offer to employ
any person who is or has been an employee of Center without prior consent from
Center.  If Client hires either an employee of Center or any person who has been
an employee of Center within six months prior to the time such person is hired
by Client, Client will be liable to Center for liquidated damages equal to six
months wages of the employee, at the rate last paid that employee by Center.
The provisions of this paragraph will survive the Term of this Agreement.

     11.  Access.
          ------

     Center and its agents will have the right of access to the Premises at any
time for the purposes of (i) making any repairs, alterations and/or inspections
which it deems necessary in its sole discretion for the preservation, safety or
improvements of the Premises, or (ii) to show the Premises to prospective
Clients, without in any way being deemed or held to have committed an eviction
(constructive or otherwise) of or trespass against Client.

     12.  Relocation.
          ----------

     Client agrees that the Center may, in its sole discretion, relocate the
Client from its present Premises to a like or similar office space within the
same Facility upon ten (10) days notice to the Client.  In the event that the
Center requires the Client to relocate, the Center will bear the reasonable
moving costs of any such relocation.  All of terms and conditions of this
Agreement, other than the designation of the Premises provided herein, will
remain unaffected and in full force and effect.

     13.  Assignment and Subletting.
          -------------------------

     No assignment or subletting of the Premises, this Agreement or any part
thereof will be made by Client without Center's prior written consent, which
consent may be withheld in Center's sole discretion.  Center may assign its
rights and its obligations under Agreement in whole or in part without Client's
consent.

     14.  Termination.
          -----------

     a.   On expiration or earlier termination of the Term, Client will, without
demand, promptly surrender and deliver the Premises, including any furniture,
fixtures and equipment provided by Center, to Center in its original condition
and configuration, reasonable wear and tear excepted.  If Client fails to so
surrender and deliver the Premises, Client agrees to pay Center, as liquidated
damages, a sum equal to twice the Monthly Office Charge for each month or
portion thereof that the Client retains possession of the Premises.

     b.   If Client vacates the Premises and leaves behind any property,
whatsoever, such property will be deemed abandoned by Client and may be disposed
of by Center at Client's expense and without liability to Center.

     c.   In the event the Premises, the Facility or the Building is damaged,
destroyed or taken by eminent domain either party may terminate this Agreement
without liability on (30) days written notice to the other party.

     d.   Upon early termination of the Main Lease, this Agreement will
terminate without liability to any party unless the Landlord under such Main
Lease elects to have this Agreement assigned to such Landlord or another entity
as provided in such Main Lease.

     15.  Default and Remedies.

     a.   Client will be deemed to be in default of this Agreement if Client
fails to fulfill any of its terms, conditions, covenants or provisions of this
Agreement, including but not limited to (1) payment of Monthly Office Charge
and/or any other charges hereunder within ten days of the date such charges
become due; or the abandonment and/or vacation of the Premises by the Client
prior to expiration of the Term, or (2) if Client becomes insolvent, makes an
assignment for the benefit of creditors or files a voluntary petition, or has an
involuntary petition filed against it, under any bankruptcy or insolvency law.

     b.   In case of such default, the Center may, at its sole discretion,
terminate this Agreement upon five days notice to the Client.  Upon the
expiration the five day period, Client will vacate the premises.  Should Client
fail to vacate the Premises, the Center may:

          i.   re-enter and take possession of the Premises and remove all
               persons and property therefrom; and

          ii.  any telephone lines installed for the benefit of Client; and

          iii. cease supplying Client with the services described in Paragraph 1
               hereof.

If Client defaults and Center takes any of the foregoing action, or changes the
locks, removes Client's property, or otherwise denies access to Client, Center
will not be liable for any damages to the Client.

     c.   In addition to the foregoing, Center may elect to accelerate all of
Client's obligations hereunder, including without limitation, Monthly Office
Charge and other monthly recurring charges, for all or part of the term.  Center
is under no obligation, implied or otherwise, to mitigate its damage(s) under a
default by Client.

     d.   Should Center be unable to enter into another office service agreement
relating to the Premises, or should Center enter into another office service
agreement relating to the Premises for less

                                       3
<PAGE>

than the Monthly Office Charge which Client is obligated to pay under this
Agreement, Client will pay the amount of such deficiency, plus the expenses of
entering into such other service agreement relating to the Premises, immediately
in one lump sum, to Center upon demand and/or at Center's option as such
obligations accrue hereunder.

     e.   In connection with any default by client under this Agreement, if
Center incurs attorney's fees and/or costs of collection or of ensuring
performance, Client will pay all such sums with interest, and such sums will be
deemed to be owed by Client in addition to the Monthly Office Charge hereunder,
and if the Term has expired at the time of incurring such sums, such sums will
be recoverable by Center as damages.

     16.  Mail & Telephone Forwarding.
          ---------------------------

     Upon expiration of the Term, Center will, unless otherwise instructed by
Client in writing no later than 30 days prior to the expiration of the Term,
forward mail to Client at its new address and give out Client's new telephone
number via a voice mail message for a period of three months at the rate of One
Hundred and Fifty Dollars ($150.00) per month, which sums will be deducted from
any amounts deposited with the Center from the refundable retainer deposited
hereunder or will otherwise be paid to the Center in advance.  Unless the Client
pays the Charge set forth herein to the Center in advance, Center will have no
obligation to provide the services set forth herein.  Except as expressly
provided herein, Center will have no obligation to notify any person or entity
of Client's new telephone number and address.

     17.  Notices.
          -------

     Any notice under this Agreement will be in writing and will be either
delivered by hand, first class mail or by overnight courier to the party at the
address set forth below.  Center hereby designates its address as:

          Austin Mopac d/b/a/ VANTAS
          ------------
          8303 North Mopac Expressway
          ---------------------------
          Austin TX 78759
          ---------------

          Attn: Management

     Client hereby designates its address (which address must be an address
within the United States), as

          Verisity Design
          ---------------
          Attn: Mike Stellfox
                -------------
          2041 Landings Drive
          -------------------
          Mountain View CA 94043
          ----------------------
          Phone: (650)-934-6800
                 --------------
          Fax: (650)-934-6801
               --------------

     If such mail is properly addressed and mailed as above, it will be deemed
notice for all purposes, given when sent or delivered, even if returned as
undelivered.

     18.  Severability.
          ------------

     The invalidity of any one or more of the sections, subsections, sentences,
clauses or words contained in this Agreement or the application thereof to any
particular set of circumstances, will not affect the validity of the remaining
portions of this Agreement or of their valid application to any other set of
circumstances.  Regardless of whether or not either party has elected to consult
with legal counsel in reviewing this Agreement, it is the intent of the parties
that in no event will the terms, conditions or provisions of this Agreement be
construed against either party as the drafter of this Agreement.

     19.  Execution by Client.
          -------------------

     The party or parties executing this Agreement on behalf of the Client
warrant(s) and represent(s):  (i) that such executing party (or parties) has (or
have) complete and full authority to execute this Agreement on behalf of Client;
and (ii) that Client will fully perform its obligations hereunder.

     20.  Miscellaneous.
          -------------

     a.   Failure of the Center to insist upon the strict performance of any
term or condition of this Agreement or to exercise any right or remedy available
for a breach thereof, or acceptance of full or partial payment during the
continuance of any such breach, will not constitute a waiver of any such breach
or any such term or condition. No term or condition of this Agreement required
to be performed by Client and no breach thereof, will be waived, altered or
modified, except by a written instrument executed by Center.

     b.   Time is of the essence as to the performance by Client of all
covenants, terms and provisions of this Agreement.

     c.   This Agreement embodies the entire understanding between the parties
relative to its subject matter, and will not be modified, changed or altered in
any respect except in writing signed by all parties.

     d.   This Agreement may be executed in two or more counterparts, each of
which will be deemed to be an original, but all of which together will
constitute one and the same instrument.

     e.   This Agreement is subject and subordinate to the Building lease
governing the Facility, under which Center is bound as tenant (the "Main Lease")
and the provisions of the Main Lease, other than as to the payment of Monthly
Office Charge or other monies, are incorporated into this Agreement as if
completely herein rewritten. Client will comply with and be bound by all
provisions of the Main Lease except that the payment of Monthly Office Charge
will be governed by the provisions of this Agreement, and Client will indemnify
and hold Center harmless from and against any claim or liability under the Main
Lease arising from Client's breach of the Main Lease or this Agreement.

     IN WITNESS WHEREOF, Center and Client have executed this Agreement as of
the date first above written.

CENTER: /s/ Valerie Allen
        -------------------------------------------------------------

By: General Manager
    -----------------------------------------------------------------

CLIENT: Verisity Design, Inc.
        -------------------------------------------------------------
(If a corporation)

By: /s/ Charles Alvarez
    -----------------------------------------------------------------

Name: Charles Alvarez
      ---------------------------------------------------------------

Title: Vice President Finance and Administration/CFO
       --------------------------------------------------------------

                                [Corporate Seal]

CLIENT:
(If an individual or partnership)

                                       4
<PAGE>

By:_________________________________________

By:_________________________________________

                                       5
<PAGE>

SCHEDULE A OPERATING STANDARDS
------------------------------

1.   Clients and their guests will conduct themselves in a businesslike manner;
     proper attire will be worn at all times; and the noise level will be kept
     to a level so as not to interfere with or annoy other Clients.

2.   Client will not provide or offer to provide any services to Center's
     customers if such services are available from Center.

3.   Client will not prop open any corridor doors, exit doors or doors
     connecting corridors during or after business hours.

4.   Clients using public areas may only do so with the consent of the Center,
     and those areas must be kept neat and attractive at all times.

5.   Client will not conduct any activity within the Premises, Facility or
     Building which in the sole judgment of the Center will create excessive
     traffic or is inappropriate to a shared office environment.

6.   Client may not conduct business in the corridors or any other areas except
     in its designated offices or conference rooms without the written consent
     of Center.

7.   All corridors, halls, elevators and stairways will not be obstructed by
     Client or used for any purpose other than normal egress and ingress.

8.   No advertisement, identifying signs or other notices will be inscribed,
     painted or affixed on any part of the corridors, doors, windows or public
     areas.

9.   Without Center's prior written consent, Client is not permitted to place
     "mass market", direct mail or advertising (i.e. newspaper, classified
     advertisements, yellow pages, billboards) using Center's assigned telephone
     number or take any such action that would generate an excessive number of
     incoming calls.

10.  Client will not solicit clients of Center or their employees in the
     Building without first obtaining Center's prior written consent.

11.  Immediately following Client's use of conference room space and/or
     audio/visual equipment, Client will clean up and return the space and
     equipment to the state and condition it was in prior to Client's use. If
     not, Center may charge Client for any other expenses required to restore
     the conference space and/or equipment to its original condition.

12.  Center must be notified in writing if Client desires to utilize the
     conference room or other common areas of the Facility during evening or
     weekend hours. Center may deny the Client access if the desired usage is
     inappropriate and may disrupt normal operations.

13.  Client will not, without Center's prior written consent, store or operate
     any computer (except a desktop/laptop computer or fax machine) or any other
     large business machines, copier and postage equipment, heating equipment,
     stove, speaker phones, radios, stereo equipment or other mechanical
     amplification equipment, refrigerator or coffee equipment, or conduct a
     mechanical business, do any cooking, or use or allow to be used on the
     Premises oil, burning fluids, gasoline, kerosene for heating, warming or
     lighting. No article deemed extra hazardous on account of fire or any
     explosives will be brought into said Premises or Facility. No offensive
     gases, odors on liquids will be permitted.

14.  Client will bring no animals into the Premises or Facility except for those
     assisting disabled individuals.

15.  Client will not remove furniture fixtures or decorative material from
     offices or common areas without the prior written consent of Center.

16.  Client will not make any additional copies of any Center issued keys. All
     keys and security cards are the property of Center and must be returned
     upon request or by the close of the business on the expiration or sooner
     termination of the Agreement term. Any lost or unreturned keys or cards
     will incur a Twenty Five Dollar ($25.00) per item charge and the cost to
     re-key the office.

17.  Client will not smoke nor allow smoking in any area of the Facility,
     including the Premises, and will comply with all governmental regulations
     and ordinances concerning smoking.

18.  Client will not allow more than three visitors in the reception lobby of
     the Premises at any one time.

19.  Client's parking rights (if any) are defined by the Main Lease.  Landlord
     reserves the right to modify parking arrangements if required to do so by
     Building management.

20.  Any alterations to the Premises requested by Client, including affixing
     anything to the walls of the Premises, will be done only (i) with the
     written permission of Center, which permission may be withheld by the
     Center for any reason whatsoever, and (ii) by an agent of the Center's
     choosing at the Client's sole cost and expense.

21.  Any equipment desired to be used and or installed by Client, other than
     those machines ordinarily used for regular office purposes (ie. personal
     computers, personal printers, calculators, adding machines, etc.) will be
     subject to the Centers prior written consent to any such use or
     installation.

22.  Client will cooperate and be courteous with all other occupants of the
     Facility and Center's staff and personnel.

                                       6
<PAGE>

23.  Upon request, Client will use a chair mat.

24.  Center reserves the right, without prior notice, to modify any of the
     foregoing and to make such other reasonable rules and regulations as in
     sole discretion may from time to time be needed for the safety, care,
     appropriate operation and cleanliness of the Facility.

                                       7
<PAGE>

Alliance
--------

Business Centers                         LEASE AND SERVICE AGREEMENT
                                         OFFICE RIDER

RE:  Lease and Service Agreement between  Verisity Design and Alliance
                                          ---------------     --------
     Business Centers ("Agreement").
     ----------------

DATE:  April 12, 1999
      -----------------

CENTER: Austin - N. Mopac, #145
       ---------------------------

Paragraph "1b" of the Agreement is hereby modified as follows:

In place and instead of facility office space number 158 Lessee shall now
                                                     ---
occupy facility office space number 173. Lessee hereby agrees and
                                    ---
understands that it no longer has a right to use and occupy facility office
space 158.
      ---

In modifying Paragraph "4a" of the Agreement, Lessee shall pay Lessor as rent
for the Premises a total rental of $8,750 (for office #173), payable in
                                   ------------------------
equal monthly installments of $1,750.00.
                              ---------

All other terms and conditions of the Agreement shall remain in full force and
effect.

ACCEPTED BY LESSOR:                   ACCEPTED BY LESSEE:

By: /s/ Valerie Allen                 By: /s/ Charles Alvarez
   -----------------------------         ----------------------------------

Date: 4/28/99                         Title: VP Finance and Admin/CFO
     ---------------------------            -------------------------------

                                      Date: 4/23/99
                                           --------------------------------
<PAGE>

Alliance
--------

Business Centers                          LEASE AND SERVICE AGREEMENT
                                          OFFICE RIDER

RE: Lease and Service Agreement between Verisity Design and Alliance
                                        ---------------     --------
    Business Centers ("Agreement").
    ----------------

DATE: April 12, 1999
     ------------------

CENTER: Austin - N. Mopac, #145
       ---------------------------

Paragraph "1b" of the Agreement is hereby modified as follows:

In place and instead of facility office space number 158 Lessee shall now
                                                     ---
occupy facility office space number 173. Lessee hereby agrees and
                                    ---
understands that it no longer has a right to use and occupy facility office
space 158.
      ---

In modifying Paragraph "4a" of the Agreement, Lessee shall pay Lessor as rent
for the Premises a total rental of $8,750 (for office #173), payable in
                                   ------------------------
equal monthly installments of $1,750.00.
                              ---------

All other terms and conditions of the Agreement shall remain in full force and
effect.

ACCEPTED BY LESSOR:                        ACCEPTED BY LESSEE:

By: /s/ Valerie Allen                      By: /s/ Charles Alvarez
   ------------------------------             --------------------------------

Date:____________________________          Title: VP Finance and Admin./CFO
                                                 -----------------------------

                                           Date: 4/23/99
                                                ------------------------------

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