Document:

<PAGE>   1
                                SECOND AMENDMENT

     THIS SECOND AMENDMENT (the "Amendment") is made and entered into as of 14
August, 2000, by and between EOP-TEN CANAL PARK, L.L.C., a Delaware limited
liability company ("Landlord"), and ASPEN TECHNOLOGY, INC. a Massachusetts
corporation ("Tenant").

                                   WITNESSETH

A.   WHEREAS, Landlord (as successor in interest to Beacon Properties, L.P.) and
     Tenant are parties to that certain lease dated the 30th day of January,
     1992, for premises currently containing approximately 110,843 rentable
     square feet of space (the "Premises") on the first (1st) through the sixth
     (6th) floors of the building commonly known as Ten Canal Park and the
     address of which is Ten Canal Park, Cambridge, Massachusetts 02141 (the
     "Building"), which lease has been previously amended by a First Amendment
     dated May 5, 1997 (collectively, the "Lease"); and

B.   WHEREAS, the Lease by its terms shall expire on September 30, 2002 ("Prior
     Termination Date"), and the parties desire to extend the Term of the Lease,
     all on the terms and conditions hereinafter set forth;

     NOW, THEREFORE, in consideration of the mutual covenants and agreements
herein contained and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, Landlord and Tenant agree as
follows;

I.   EXTENSION. The Lease Term is hereby extended for a period of 120 months and
     shall expire on September 30, 2012 ("Extended Termination Date"), unless
     sooner terminated in accordance with the terms of the Lease. That portion
     of the Lease Term commencing the day immediately following the Prior
     Termination Date ("Extension Date") and ending on the Extended Termination
     Date shall be referred to herein as the "Extended Term." Tenant
     acknowledges that this extension is in fulfillment of Tenant's options to
     extend contained in Paragraph 1 of Exhibit D to the Lease and, accordingly,
     that said Paragraph 1 shall be no further force of effect.

II.  MONTHLY BASIC RENT. As of the Extension Date, the schedule of monthly
     installments of Basic Rent payable with respect to the Premises during the
     Extended Term is the following:

          A.   Sixty (60) equal installments of Three Hundred Forty-One Thousand
               Seven Hundred Sixty-Five and 92/100 Dollars ($341,765.92) each
               payable on or before the first day of each month during the
               period beginning October 1, 2002 and ending September 30, 2007.

          B.   Sixty (60) equal installments of Three Hundred Forty-Eight
               Thousand Six Hundred Ninety-Three and 60/100 Dollars
               ($348,693.60) each payable on or before the first day of each
               month during the period beginning October 1, 2007 and ending
               September 30, 2012.

     All such Basic Rent shall be payable by Tenant in accordance with the terms
     of Section 3.1 of the Lease.

III. ESCALATION CHARGES. For the period commencing on the Extension Date and
     ending on the Extended Termination Date, Tenant shall pay the Escalation
     Charges for the Premises as set forth in the Lease.

IV.  IMPROVEMENTS TO PREMISES.

     A.   CONDITION OF PREMISES. Tenant is in possession of the Premises and
          accepts the same "as is" without any agreements, representations,
          understandings, or obligations on the part of Landlord to perform any
          alterations, repairs or improvements, except as may be expressly
          provided otherwise in this Amendment.
<PAGE>   2
     B.  Cost of improvements to Premises. Any construction, alterations or
         improvements made to the Premises shall be made at Tenant's sole cost
         and expense.

V.  SECURITY DEPOSIT.

         A security deposit in the amount of $683,531.84 ("Security Deposit")
    shall be delivered to Landlord no later than September 1, 2000 by Tenant and
    shall be held by Landlord without liability for interest (unless required by
    law) as security for the performance of Tenant's obligations. All or part of
    the Security Deposit may be in the form of an irrevocable letter of credit
    (the "Letter of Credit"), which Letter of Credit shall: (a) be in the amount
    of $683,531.84; (b) be issued on the form attached hereto as Exhibit A; (c)
    name Landlord as its beneficiary; (d) be drawn on an FDIC insured financial
    institution satisfactory to the Landlord; and (e) expire no earlier than
    sixty (60) days after the Termination Date of this Lease. If Landlord
    intends to assign Landlord's interest in the Lease, Tenant shall, upon
    notice from Landlord, deliver to Landlord an amendment to the Letter of
    Credit naming Landlord's assignee as the beneficiary thereof. If Tenant
    fails to deliver such amendment within seven (7) days after notice from
    Landlord, Landlord shall have the right to draw down the entire amount of
    the Letter of Credit and hold the proceeds thereof as a Security Deposit in
    accordance with this Section V. The Security Deposit is not an advance
    payment of Rent or a measure of Tenant's liability for damages. Landlord
    may, from time to time, without prejudice to any other remedy, use all or a
    portion of the Security Deposit to satisfy past due Rent or to cure any
    uncured default by Tenant. If Landlord uses the Security Deposit, Tenant
    shall on demand restore the Security Deposit to its original amount (which
    may be achieved by providing an additional letter of credit for the amount
    so drawn), Landlord shall return any unapplied portion of the Security
    Deposit to Tenant within 45 days after the last to occur of: (1) the
    determination of Tenant's Escalation Charge for the final year of the Term;
    (2) the date Tenant surrenders possession of the Premises to Landlord in
    accordance with this Lease; or (3) the Termination Date. If Landlord
    transfers its interest in the Premises, Landlord may assign the Security
    Deposit to the transferee and, following the assignment, provided that (i)
    Landlord provides the Tenant with notice of such transfer, and (ii) such
    transferee assumes Landlord's obligations with respect to the Security
    Deposit, Landlord shall have no further liability for the return of the
    Security Deposit. Landlord shall not be required to keep the Security
    Deposit separate from its other accounts.

         Notwithstanding anything herein to the contrary, the Security Deposit
    will be adjusted each November 1, beginning November 1, 2003, as follows:
    Tenant will inform Landlord by October 15 of each year (i) of the ratio, as
    of October 1, of the current assets of Tenant to the current liabilities of
    Tenant, determined in accordance with generally accepted accounting
    principles, consistently applied (United States) ("Tenant's Current Ratio"),
    and (ii) whether Tenant has shown a net profit, determined in accordance
    with generally accepted accounting principles, consistently applied (United
    States), for the quarter ending on the previous September 30. If Tenant's
    Current Ratio is less than 2.0:1, or if Tenant has not shown a net profit
    for the quarter ending on the previous September 30, then Tenant shall
    provide Landlord with an additional Security Deposit of $341,765.92,
    provided that the Security Deposit shall never exceed $1,025,297.76.
    Beginning November 1, 2005, if Tenant's Current Ratio is greater than 2.0:1,
    and if Tenant has shown a net profit for the quarter ending on the previous
    September 30, then provided Tenant is not in default beyond any applicable
    notice and cure periods under this Lease as of the effective date of any
    reduction of the Security Deposit, the Security Deposit shall be reduced by
    $341,765.92. In all events, a certificate of Tenant, executed by Tenant's
    chief executive officer or Tenant's chief financial officer, shall be
    sufficient to establish such ratio in any instance.

VI. Renewal Option

    A. Tenant shall have the right to extend the Lease Term (the "Renewal
Option") for one additional period of 5 years commencing on the day following
the Extended Termination Date of the Lease Term and ending on the 5th
anniversary of the Extended Termination Date (the "Renewal Term"), if:

                                      -2.
<PAGE>   3
     1. Landlord receives notice of exercise ("Renewal Notice") not less then
     twenty-four (24) full calendar months prior to the Extended Termination
     Date and not more than twenty-seven (27) full calendar months prior to the
     Extended Termination Date; and

     2. Tenant is not in default under the Lease beyond any applicable cure
     periods at the time that Tenant delivers its Renewal Notice (hereinafter
     defined); and

     3. Not more than twenty-five percent (25%) of the Premises is sublet at the
     time that Tenant delivers its Renewal Notice;

     4. If applicable, the Renewal Notice shall not apply to any part of the
     Premises that is sublet at the time that Tenant delivers its Renewal Notice
     (in other words, Tenant can only renew the Lease with respect to those
     portions of the Premises which have not been sublet); and

     5. The Lease has not been assigned prior to the date that Tenant delivers
     its Renewal Notice (but the foregoing prohibition shall not apply to an
     assignment of the Lease to(i) an entity directly or indirectly controlling,
     controlled by or under common control with Tenant; (ii) any entity owning
     or controlling fifty percent (50%) or more of the outstanding voting
     interests of Tenant; (iii) any entity of which Tenant owns or controls
     fifty percent (50%) or more of the voting interests; (iv) any entity into
     which Tenant is merged or consolidated; (v) any corporation or other entity
     resulting from the consolidation of Tenant with some other entity; or (vi)
     a successor corporation or some other entity arising from any bona fide
     reorganization of Tenant (each of the entities described in (i)-(vi) being
     hereafter referred to as an "Affiliate"), provided that such Affiliate
     agrees directly with Landlord to be bound by all obligations of Tenant
     under the Lease).

     Upon the timely giving of the Renewal Notice, the term of the Lease shall
be extended for the Renewal Term without the need for further act or deed of
either party, upon all of the same terms and conditions of the Lease as are in
effect immediately preceding the Renewal Term, except that the Basic Rent
payable during the Renewal Term shall be as set forth in Paragraph B of this
Section VI, and determined in accordance with Paragraph D of this Section VI. If
Tenant fails timely to give the Renewal Notice, Tenant shall have no further
right to renew the term of the Lease pursuant to this Section VI, time being of
the essence of this Section VI.

     B. The Basic Rent rate per rentable square foot for the Premises during the
Renewal Term shall equal the Fair Market Rental Value, as defined in Paragraph 4
of Section 1 of Exhibit D to the Lease, provided however, that in no event shall
the sum of Basic Annual Rent and Escalation Charges payable by Tenant for any
twelve-(12)-month period during the Renewal Term be less than the sum of Basic
Annual Rent and Escalation Charges payable by Tenant in respect of the
twelve-(12)-month period immediately preceding the commencement of the Renewal
Term.

     C. Tenant shall pay Escalation Charges for the Premises during the Renewal
Term in accordance with the terms and conditions of the Lease.

     D. Within thirty (30) days after receipt of Tenant's Renewal Notice,
Landlord shall advise Tenant of Landlord's designation of the applicable Basic
Rent rate for the Premises for the renewal Term. Tenant, within thirty (30) days
after the date on which Landlord advises Tenant of the applicable Basic Rent
rate for the Renewal Term, shall either (i) give Landlord final binding written
notice ("Acceptance Notice") that it has accepted Landlord's designation, or
(ii) if Tenant disagrees with Landlord's designation, provide Landlord with
written notice ("Arbitration Notice") submitting Tenant's disagreement to
arbitration in accordance with the procedures set forth in the paragraph
entitled "Dispute as Fair Market Rent" in Paragraph 1 of Exhibit D of the Lease.
If Tenant fails to provide Landlord with either an Acceptance Notice or an
Arbitration Notice within such thirty (30) day period, Tenant shall conclusively
be deemed to have accepted Landlord's designation of the Basic Rent rate for the
Renewal Term. If Tenant timely gives an Arbitration Notice, then, unless the
parties otherwise agree in writing, the decision of the arbitrators, in
accordance with said Paragraph 1 of Exhibit D to the Lease, shall be conclusive

                                      -3-
<PAGE>   4
and binding upon the parties.

      E.   If Tenant is entitled to and properly exercises its Renewal Option,
the parties shall, promptly after the Basic Rent for the Renewal Term is
determined in accordance with Paragraph D above, execute an amendment (the
"Renewal Amendment") to confirm the exercise of Tenant's Renewal Option and
reflecting only changes in the Basic Rent, Lease Term, Termination Date and
other appropriate terms. The execution of the Renewal Amendment shall not be a
condition to the exercise by Tenant of Tenant's Renewal Option (the parties
hereby acknowledging and agreeing that the timely giving of Tenant's Renewal
Notice and the satisfaction of all of the conditions to the exercise of Tenant's
Renewal Option, as set forth in Paragraph A above, shall be sufficient to bind
both parties to the exercise of Tenant's Renewal Option).

VII   Other Pertinent Provisions. Landlord and Tenant agree that, effective as
      of the date hereof (unless different effective date(s) is/are specifically
      referenced in this Section), the Lease shall be amended in the following
      additional respects:

      A. NOTICES

         For all purposes of the Lease, the notice address for the Landlord is
         as follows:

         EOP-One Canal Park, L.L.C.
         c/o Equity Office Properties
         245 First Street
         Cambridge, Massachusetts 02142
         Attention: Building Manager

         With copy to:

         Equity Office Properties
         Two North Riverside Plaza
         Suite 2200
         Chicago, Illinois 60606
         Attention: Northeast Regional Counsel Equity Office Properties

         For all purposes of the Lease, the notice address for Tenant is as
         follows:

         Aspentech
         Ten Canal Park
         Cambridge, MA 02141
         Attn: Facilities Manager

         With copy to:

         Bingham Dana LLP
         150 Federal Street
         Boston, MA 02110
         Attn: Henry S. Healy, Esq.

     B.  Section 14.29 is hereby deleted in its entirety and of no further force
         or effect.

     C.  The phrase "(including the Fixed Management Fee, as said term is
         defined in Section 14.29 of the Lease)" is hereby deleted from
         Paragraph B.1 of Exhibit E to the Lease, and replaced with the
         following: "(including a management fee not to exceed four percent (4%)
         of gross revenues)".

VIII. Miscellaneous.

     A.  This Amendment sets forth the entire agreement between the parties with
         respect to the matters set forth herein. There have been no additional
         oral or written representations or agreements. Under no circumstances
         shall Tenant be entitled to any Rent abatement, improvement allowance,
         leasehold improvements, or other work to the Premises, or any similar
         economic incentives that may have been

                                      -4.

<PAGE>   5
     provided Tenant in connection with entering into the Lease, unless
     specifically set forth in this Amendment.

B.   Except as herein modified or amended, the provisions, conditions and terms
     of the Lease shall remain unchanged and in full force and effect.

C.   In the case of any inconsistency between the provisions of the Lease and
     this Amendment, the provisions of this Amendment shall govern and control.

D.   Submission of this Amendment by Landlord is not an offer to enter into this
     Amendment but rather is a solicitation for such an offer by Tenant.
     Landlord shall not be bound by this Amendment until Landlord has executed
     and delivered the same to Tenant.

E.   The capitalized terms used in this Amendment shall have the same
     definitions as set forth in the Lease to the extent that such capitalized
     terms are defined therein and not redefined in this Amendment.

F.   Tenant hereby represents to Landlord that Tenant has dealt with no broker
     in connection with this Amendment other than the Trammell Crow Company.
     Tenant agrees to indemnify and hold Landlord, its members, principals,
     beneficiaries, partners, officers, directors, employees, mortgagee(s) and
     agents, and the respective principals and members of any such agents
     (collectively, the "Landlord Related Parties") harmless from all claims of
     any brokers claiming to have represented Tenant in connection with this
     Amendment other than the Trammell Crow Company. Landlord hereby represents
     to Tenant that Landlord has dealt with no broker in connection with this
     Amendment other than the Trammell Crow Company. Landlord agrees to
     indemnify and hold Tenant, its members, principals, beneficiaries,
     partners, officers, directors, employees, and agents, and the respective
     principals and members of any such agents (collectively, the "Tenant
     Related Parties") harmless from all claims of any brokers claiming to have
     represented Landlord in connection with this Amendment other than the
     Trammell Crow Company. Landlord agrees to pay Trammell Crow Company a
     brokerage commission in accordance with a separate written agreement
     between Landlord and Trammell Crow Company.

                                      -5-
<PAGE>   6
     IN WITNESS WHEREOF, Landlord and Tenant have duly executed this Amendment
as of the day and year first above written.

WITNESS/ATTEST:                        LANDLORD:

                                       EOP-TEN CANAL PARK, L.L.C., A Delaware
                                       limited liability company

                                          By: EOP Operating Limited Partnership,
                                              a Delaware limited partnership,
                                              its sole member

                                            By: Equity Office Properties Trust,
                                                a Maryland real estate invest-
                                                ment trust, its managing
                                                general partner
/s/ Kim Ruby
-------------------------------------
Name (print):  Kim Ruby                    By: /s/ Maryann G. Suydam
             ------------------------          ---------------------------------

-------------------------------------      Name:  Maryann G. Suydam
                                                --------------------------------

Name (print): -----------------------      Title: Regional Senior Vice President
                                                  ------------------------------

WITNESS/ATTEST:                            TENANT:
                                           ASPEN TECHNOLOGY, INC., a
                                           Massachusetts corporation

-------------------------------------      By: /s/
                                               ---------------------------------

Name (print): -----------------------      Name: -------------------------------

-------------------------------------      Title: ------------------------------

Name (print): -----------------------

                                      -6-<PAGE>   1
                                                                   Exhibit 10.16

[FLEET LOGO]

September 21, 1999

Ms. Lisa Zappala
Treasurer and Chief Financial Officer
Aspen Technology, Inc.
Ten Canal Park
Cambridge, MA 02141

Dear Lisa:

Reference is hereby made to the Further Amended and Restated Revolving Credit
Agreement dated February 15, 1996 and the First Amendment to Further Amended
and Restated Revolving Credit Agreement (collectively referred to as the
"Agreement"), by and among Aspen Technology, Inc. (Aspen) and its wholly owned
subsidiaries Process Modeling Investment Corporation, Industrial Systems, Inc.,
and Aspen Tech, Inc. (formerly Setpoint, Inc.) and successor in interest to
Dynamic Matrix Control Corporation (Aspen and such subsidiaries being
hereinafter collectively referred to as the "Borrowers"), as joint and several
borrowers, and Fleet National Bank, successor to Fleet Bank of Massachusetts,
N.A. ("Fleet" or the "Bank").

You have informed the Bank that for the periods ended March 31, 1999 and June
30, 1999 the Borrower was in violation of Consolidated EBTA (Section 7.2),
Leverage Ratio (Section 7.3) and Interest Coverage Ratio (Section 7.5). The
Bank hereby waives the violations cited above for the periods ended March 31,
1999 and June 30, 1999.

In addition, the financial covenants have been amended as shown below and
become effective with the quarter ending September 30, 1999 and thereafter,
unless otherwise indicated. The definitions used in this letter are the same as
those in the Revolving Credit Agreement.

-   Consolidated EBTA (Section 7.2): no longer required

-   Leverage Ratio (Section 7.3): no longer required

-   Quick Ratio (Section 7.4): Must be greater or equal to 2.00:1.00. The
    definition of Quick Ratio will be cash, short-term marketable securities and
    current accounts receivables and eligible installment receivables divided by
    current liabilities which includes borrowings and letters of credit issued
    under the revolver less current deferred revenues and deferred taxes.

-   Interest Coverage Ratio (Section 7.5): no longer required

-   Tangible Net worth (TNW): A minimum of $110,000,000. Tangible Net Worth is
    defined as Stockholders Equity less Intangibles and Capitalized Software.

Effective with the receipt of this letter, we will secure the obligations of
Aspen Technology, Inc. with marketable securities currently managed by Fleet
Investment Advisors. Advance rates for loans and letters of credit secured by
marketable securities are shown below. The attached Deposit Pledge Agreement
should be completed, signed and returned to us along with this letter.

<TABLE>
<CAPTION>
-------------------------------------------------------------------
Types of Securities                                  Advance Rate
-------------------------------------------------------------------
<S>                                                  <C>
U.S. Treasury Obligations (bills, notes & bonds)          90%
-------------------------------------------------------------------
Investment Grade Commercial Paper                         80%
-------------------------------------------------------------------
Federal Government or Quasi-Government Agency             80%
-------------------------------------------------------------------
</TABLE>

<PAGE>   2
<TABLE>

<S>                                                      <C>
Securities, to include those issued by GNMA, FNMA,
or FHLMC
-------------------------------------------------------------
Municipal Bonds                                           80%
-------------------------------------------------------------
Investment Grade Bonds (Moody's Aaa down through
Baa3; S&P AAA down through BBB-)                          70%
-------------------------------------------------------------
</TABLE>

In granting the waivers and amendments as outlined above, there is a one-time
fee of $10,000 payable upon signed receipt of this letter.

Upon receipt of your acceptance of this waiver and amendment letter, these
terms shall become effective. This letter waives and amends only the sections
referenced above and should not be considered a waiver or amendment of any
other terms of the Agreement. In addition, the statements, representations and
warranties made in the Agreement continue to be correct as of the date hereof
and the Borrower is in compliance with all terms of the Agreement. Except as
expressly affected hereby, the Agreement remains in full force and effect as
heretofore.

The Borrower represents and warrants that the execution of this waiver and
amendment letter has been duly authorized by the Borrower by all necessary
corporate and other action and that the execution will not conflict with,
violate the provisions of, or cause a default or constitute an event which,
with the passage of time or giving of notice or both, could cause a default on
the part of the Borrower under its charter documents or by-laws or under any
contract, agreement, law, rule, order, ordinance, franchise, instrument or
other document, or result in the imposition of any lien or encumbrance on any
property or asset of the Borrower. In addition, the statements, representations
and warranties made in the Agreement continue to be correct as of the date
hereof and the Borrower is in compliance with all terms of the Agreement.
Except as expressly affected hereby, the Agreement remains in full force and
effect as heretofore.

Sincerely,
Fleet National Bank

/s/ Olaperi Onipede
-------------------
Olaperi Onipede                         Agreed and Accepted: /s/ Lisa W. Zappala
Vice President                                               -------------------
High Technology Division                                 by: Lisa W. Zappala
                                                      title: Sr. V.P. & CFO
<PAGE>   3
FLEET BANK LOGO                                         DEPOSIT PLEDGE AGREEMENT

     THIS AGREEMENT is made as of October 18, 1999,
                                  ----------   --
by and between Aspen Technology, Inc. (the "Pledgor")
               ----------------------
               10 Canal Park
               -------------
               Cambridge, MA 02141
               -------------------

and Fleet Bank of Massachusetts, National Association (the "Bank"), 26 State
Street, Boston, Massachusetts 02109.

     In order to induce the Bank to enter into the agreement described below,
Pledgor, for good and valuable consideration, the receipt and sufficiency of
which are hereby acknowledged, hereby assigns to the Bank and grants to the
Bank a security interest in, and exclusive control over Collateral as described
below in an amount of not less than $30,000,000. The Collateral is pledged to
secure performance of all obligations, direct or indirect absolute or
contingent, now existing or hereafter arising of every kind and description
(the "Obligations"), pursuant to the  See bottom of page   dated
                                     --------------------        ---------------
between Pledgor and the Bank (the "Agreement").

COLLATERAL:  1) Securities set forth in Exhibit A attached hereto:

                /X/ in Account No. 0001479670 maintained with Bank or with the
                                   ----------
                    following institution:                                     ;
                                           ------------------------------------

                / / recorded on the books and records of the Bank, its Nassau
                    and London branches or its International Banking Facility.

The Pledgor and the Bank agree that the above pledge, and security interest
granted herewith, are subject to all of the following terms and conditions.

     1.  COLLATERAL.  The Collateral shall remain in the control or possession
of the Bank and shall constitute continuing collateral security for the full
payment and performance of the Obligations. The Pledgor agrees that so long as
any of the obligations remains outstanding no action of any kind whatsoever may
be taken by Pledgor or any other person with respect to any portion of the
Collateral without the Bank's written consent. The Bank is hereby authorized
and appointed as agent and attorney-in-fact of the Pledgor, which appointment
is coupled with an interest and shall be irrevocable so long as any of the
Obligations remains outstanding, to sign and deliver such documents,
indorsements and instruments and to take all such other actions in the name of
the Pledgor as the Bank may deem necessary or advisable to perfect or
preserve its security interest in and lien on the Collateral. In the event that
any of the Obligations shall be secured by the pledge of deposits placed with
another financial institution or with the Bank's London or Nassau branch, the
Pledgor agrees to execute and deliver a notice and acknowledgement of
assignment of deposits with respect to such Collateral in form and substance
satisfactory to the Bank.

     2.  WAIVERS BY PLEDGOR. The Pledgor waives notice of acceptance hereof,
notice of any action taken or omitted by the Bank in reliance hereon, notice of
default with respect to any of the Obligations and, to the fullest extent it
may effectively do so under applicable law, all defenses which might at any
time be available to a guarantor or surety of Obligations of the Borrower.

     3.  PLEDGE UNCONDITIONAL. This agreement is the direct, unconditional,
absolute and primary obligation of the Pledgor, and no invalidity,
irregularity or unenforceability of all or any part of the Obligations or of
any security therefor shall affect, impair or be a defense to this Agreement.
This Agreement and the Collateral are given to secure payment, and not merely
collection of the Obligations. The Bank shall not be required to seek to
enforce any of its rights under this Agreement as a condition to exercise or to
enforce its rights hereunder nor shall any failure to seek to enforce any such
rights affect, impair or be a defense to the Bank's rights hereunder.

     4.  DEFAULTS AND REMEDIES. Each of the following shall constitute a
default hereunder: any failure by the Pledgor to pay, perform or observe any
obligations on its part hereunder, the service upon the Bank, its International
Banking Facility, its Nassau branch or its London branch, or upon any other
financial institution in which the Collateral is located, of any summons naming
the Bank or such facility or branch as trustee for the Pledgor or the Borrower,
or of any similar writ or process of attachment relating to any deposit or
property of the Pledgor. Upon the occurrence of any default hereunder, the Bank
may apply any Collateral to the satisfaction of any or all of the Obligations
and pursue any additional rights or remedies available to it hereunder, or
under the Agreement or applicable law.

*Further Amended and Restated Revolving Credit Agreement dated February 15,
1996, the First Amendment dated 12/31/96 and Letter Amendments dated 12/24/98
and 9/21/99.
<PAGE>   4
     5.   REPRESENTATIONS AND WARRANTIES. The Pledgor represents and warrants to
the Bank that except for the securities interest granted to the Bank hereunder,
the Collateral is and shall remain free from any adverse lien, security interest
or encumbrances in favor of others: [if a corporation] it is duly organized,
validly existing and in good standing under the laws of Delaware and is duly
qualified to do business as foreign corporation and in good standing under the
laws of each other jurisdiction in which its business conducted or properties
owned requires such qualification; it has full power to enter into and perform
this Agreement and has taken a necessary corporate or other action to authorize
the execution, delivery and performance of this Agreement; this Agreement
constitutes the legal, valid and binding obligations of the Pledgor, enforceable
in accordance with its terms, subject to bankruptcy, insolvency or other similar
laws affecting the rights of creditors generally, the execution, delivery and
performance of this Agreement will not violate any provision of any existing
law, treaty or regulation applicable to the Pledgor or (as applicable) of its
Certificate of Incorporation, Articles of Organization and By-Laws, Articles of
Partnership trust agreement or other governing documents, or of any order or
decree of any court, arbitrator or governmental agency or of any contractual
undertaking to which it is a party or by which it may be bound; no consents,
licenses, approvals of authorizations of, exemptions by or registrations or
declarations with, any governmental authority are required with respect to this
Agreement.

     6.   COSTS. The Pledgor agrees to reimburse the Bank for any out-of-pocket
costs or expenses (including without limitation reasonable fees and
disbursements of counsel) incurred by the Bank in connection with the
preservation or enforcement of its rights or remedies under this Agreement or
any agreement between Borrower and the Bank.

     7.   INTERPRETATION, ETC. This Agreement is a continuing one and all
liabilities to which it applies or may apply under the terms hereof shall be
conclusively presumed to have been created in reliance hereon. No delay on the
part of the Bank in exercising any of its options, powers or rights, or partial
or single exercise thereof, shall constitute a waiver thereof. Except as
expressly provided herein, no waiver of any of its rights and no modification or
amendment of this Agreement shall be deemed to be made by the Bank unless the
same shall be in writing, duly signed on behalf of the Bank, each such waiver
[if any] shall apply only with respect to the specific instance involved and
shall in no way impair the rights of the Bank or the obligations of the Pledgor
to the Bank in any other respect or at any other time. The Collateral this
Agreement and the rights and obligations of the Bank and of the Pledgor
hereunder shall be governed by and construed in accordance with the laws of the
Commonwealth of Massachusetts. This Agreement is binding upon the Pledgor, its
successors and assigns and shall inure to the benefit of the Bank and its
respective successors or assigns including [without limitation] any other holder
at any time of the Note or any of them. The headings contained herein are for
convenience only and shall not affect the construction hereof. If any provision
hereof is prohibited or unenforceable in any jurisdiction, the same shall not
affect the remaining provisions hereof nor affect the validity or enforceability
of such provision in any other jurisdiction.

     6.   SUBMISSION TO JURISDICTION. Pledgor irrevocably submits to the
non-exclusive jurisdiction of any state or federal court sitting in Boston,
Massachusetts over any suit, action or proceeding arising out of or relating to
this Agreement or the Collateral. Pledgor irrevocably waives, to the fullest
extent it may effectively do so under applicable law, its right to a trial by
jury, and any objection which it may have or hereafter have to the laying of the
venue of any such suit, action or proceeding brought in any such court and any
claim that any such suit, action or proceeding brought in any such court has
been brought in an inconvenient forum. Pledgor agrees, to the fullest extent it
may effectively do so under applicable law that a final judgment in any such
suit, action or proceeding brought in such court shall be conclusive and binding
upon Pledgor and may be enforced in the courts of the United States of America
and the Commonwealth of Massachusetts for any other courts to the jurisdiction
of which the Pledgor is or may be subject) by a suit upon such judgment,
provided that service process is effected on Pledgor as permitted by law.

     IN WITNESS WHEREOF, the Pledgor has caused this Agreement to be duly
executed under seal and delivered as of the date first above written.

                                             /s/ Aspen Technology, Inc.
                                             --------------------------

                                             By: /s/ Lisa W. Zappala
                                             --------------------------
Agreed and Accepted:
FLEET BANK OF MASSACHUSETTS,                 Lisa Zappala, SVP & CFO
NATIONAL ASSOCIATION                         --------------------------
                                             (Print name & Title)
By:
    ------------------------------

----------------------------------
(Print Name & Title)

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