Document:

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                                                                   EXHIBIT 10.47

                             SECURED PROMISSORY NOTE

$10,000,000                                                        June 25, 1998

     FOR VALUE RECEIVED, the undersigned, I3S Inc. ("Borrower"), hereby promises
to pay to ASCEND COMMUNICATIONS, INC. ("Lender"), or order, the principal sum or
so much of the principal sum of Ten Million Dollars ($10,000,000) as may from
time to time have been advanced and be outstanding, together with accrued
interest as provided herein.

A.   Equipment Acquisition Facility.

     1. Advances. Borrower may from time to time request advances from Lender
for the purpose of financing Borrower's acquisition of equipment (individually
an "Equipment Advance" and collectively the "Equipment Advances") by giving
written notice to Lender in accordance with the terms hereof, which notice shall
indicate (i) the amount of the Equipment Advance requested and (ii) the
equipment (the "Financed Equipment") and the purchase price thereof, to be
acquired with the Advance proceeds. An Equipment Advance may not exceed one
hundred percent (100%) of the invoice cost of the Financed Equipment, including
all capitalized labor pertaining thereto, that is to be acquired with such
Equipment Advance. Provided that (i) no Event of Default exists, (ii) the
requested Equipment Advance would not cause an Event of Default to occur, and
(iii) Borrower's gross revenues or earnings before interest, taxes, depreciation
and amortization ("EBITDA") for the immediately preceding fiscal quarter of
Borrower was not less fifty percent (50%) of Borrower's projected gross revenues
or EBITDA for such fiscal quarter as set forth in the business plan attached
hereto as Attachment A, Lender shall make the Equipment Advance to Borrower
within five (5) days of receipt of (A) Borrower's notice, (B) Borrower's written
representation and warranty that the Financed Equipment that is be financed with
the Equipment Advance will be acquired by Borrower free and clear of all Liens,
except for the Lien created hereunder and Permitted Liens, to the extent that
such Liens were not imposed on the Financed Equipment for the benefit of
creditors of parties other than Borrower, and (C) the purchase invoices and
other sales documents relating to the Financed Equipment that is to be financed
with the Equipment Advance. Without Lender's prior consent, Lender shall not be
obligated to make an Equipment Advance (i) for an amount less than One Million
Dollars ($1,000,000), (ii) if the total number of Equipment Advances made would
exceed six (6), (iii) after October 1, 1999, or (iv) to the extent that such
Equipment Advance, when aggregated with all prior Equipment Advances, would
exceed Ten Million Dollars ($10,000,000). Borrower shall not have the right to
re-borrow any Equipment Advance to the extent that it has been repaid. All
Equipment Advances made during a calendar month for purposes hereof shall be
aggregated as the Calendar Month Advances.

     2.   Interest.

          (a) Interest Rate. Interest shall accrue with respect to the principal
sum of the Calendar Month Advances at the per annum rate equal to the "Prime
Rate" as listed in The Wall

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Street Journal Money Rates report from time to time during the term hereof (the
"Prime Rate"). However, if an Event of Default, as defined herein, occurs, then
interest shall accrue at the rate per annum equal to two percent (2%) plus the
rate that would otherwise be in effect (the "Default Rate"). Interest payable
hereunder with respect to the Calendar Month Advances shall be calculated on the
basis of a three hundred sixty (360) day year for actual days elapsed. Each
change in the Prime Rate shall result in a change in the interest rate with
respect to the Calendar Month Advances as of the date of such Prime Rate change,
without any notice to Borrower.

          (b) Interest Payments. Interest shall be due and payable with respect
to a Calendar Month Advance in arrears on the first day of each calendar month,
commencing with the twelfth (12th) month after the date of the calendar month
relating to such Calendar Month Advance (such month the "Related Calendar
Month"); provided, however, that if Borrower is Cash Flow Positive (as defined
herein) for any calendar month commencing after the Related Calendar Month, then
interest shall be due and payable in arrears with respect to such Calendar Month
Advance on the first day of each calendar month commencing with the first (1st)
month after the month for which Borrower was Cash Flow Positive (Borrower shall
have a ten (10) day grace period with respect to the first interest payment due
in accordance with this proviso). Borrower is "Cash Flow Positive" for a
calendar month if Borrower's earnings before interest, taxes, depreciation and
loan amortization for such month, all as determined in accordance with generally
accepted accounting principles, consistently applied, exceed zero.

     3.   Principal Payments.

          (a) Scheduled Payments. The principal indebtedness of a Calendar Month
Advance shall be payable in twenty-four (24) monthly installments, based on a
two (2) year amortization for a two (2) year term, with the first installment
due on the first day of the twelfth (12th) calendar month commencing after the
Related Calendar Month for such Calendar Month Advance. All interest accrued but
unpaid with respect to an Equipment Advance shall be due and payable with the
twenty-fourth (24th) principal installment thereof.

          (b) Mandatory Prepayment. The principal indebtedness and all accrued
but unpaid interest with respect to the Calendar Month Advances shall become
immediately due and payable, without demand or any notice by Lender, on the date
of the first to occur of (i) the effective date of the IPO or (ii) the date of a
Change of Control.

     4.   Fee. If any principal of an Equipment Advance or accrued but unpaid
interest with respect to the Equipment Advances is outstanding on the first
twelve month anniversary of the date of the first Equipment Advance hereunder
(the "Anniversary Date"), then, as of the Anniversary Date, Lender shall have
fully-earned a fee (the "Fee") equal to five percent (5%) of the aggregate
amount of the principal outstanding and interest accrued and unpaid as of the
Anniversary Date. Borrower shall pay the Fee to Lender in full on or before the
expiration of five (5) business days after the Anniversary Date.

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     5.   General Payment Provisions.

          (a)  Optional Prepayment. Borrower shall have the right at any time
and from time to time to prepay, in whole or in part, the principal of the
Calendar Month Advances, without payment of any premium or penalty. Any
principal prepayment shall be accompanied by a payment of all interest accrued
on the amount prepaid through the date of such prepayment.

          (b)  Form of Payment. Principal and interest and all other amounts
due under with respect to the Calendar Month Advances are to be paid in lawful
money of the United States of America in federal or other immediately available
funds.

B.   Covenants.

     1.   Insurance. Borrower, at its expense and with such companies as are
reasonably acceptable to Lender, shall maintain liability insurance and fire,
theft and other hazard insurance which covers the Collateral, which insurance
shall be in such amounts as are ordinarily carried by other owners in similar
businesses conducted in the locations where Borrower's business is conducted on
the date hereof. All such liability insurance policies shall show Lender as an
additional insured or loss payee, as applicable, and shall specify that the
insurer must give at least thirty (30) days' notice to Lender before canceling
its policy for any reason. Borrower, upon Lender's request, shall deliver to
Lender certified copies of such policies of insurance and evidence of the
payments of all premiums therefor.

     2.   Financial Information. Borrower shall deliver to Lender:

          (a) as soon as practicable after the end of each fiscal quarter of
each Fiscal Year, and in any event within thirty (30) days thereafter, an
unaudited balance sheet of Borrower as of the end of such fiscal quarter, cash
flow statements and an unaudited statement of operations of Borrower for the
portion of the Fiscal Year ended with such fiscal quarter prepared and certified
by the principal financial or accounting officer of Borrower, subject, however,
to the exclusion of footnotes and to normal year-end audit adjustments, and a
comparison of such statements to Borrower's operating plan or budget then in
effect;

          (b) as soon as practicable after the end of each Fiscal Year, and in
any event within ninety (90) days thereafter, a copy of its audited financial
statements accompanied by a report thereon by a firm of independent certified
public accountants selected by Borrower, which report shall state that such
financial statements fairly present Borrower's financial position at the end of
such Fiscal Year;

          (c) as soon as available, and in any event within thirty (30) days
after the commencement of each Fiscal Year, a budget and business plan for
Borrower for such Fiscal Year;

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          (d)  promptly upon their becoming available, one copy of each report,
notice or proxy statement sent by Borrower to its shareholders generally and of
each regular or periodic report or registration statement, prospectus or written
communication (other than transmittal letters) filed by Borrower with the
Securities and Exchange Commission or any securities exchange on which
Borrower's securities are listed; and

          (e)  with reasonable promptness, such other information as from time
to time may be reasonably requested by Lender.

C.   Security Interest.

     1.   Grant of Security Interest. Borrower grants to Lender a security
interest in the Collateral, as defined herein, to secure the payment of all of
the indebtedness hereunder (the "Secured Obligations").

     2.   Representations and Warranties Regarding Collateral. Borrower
represents and warrants to Lender that Borrower is the true and lawful owner of
the Collateral, having good and marketable title thereto, free and clear of any
and all Liens other than the Lien and security interest granted to Lender
hereunder and Permitted Liens, including, without limitation, those as described
in Attachment "B" hereto. Borrower shall not create or assume or permit to exist
any such Lien on or against any of the Collateral except as created or permitted
by this Note and Permitted Liens, and Borrower shall promptly notify Lender of
any such other Lien against the Collateral and shall defend the Collateral
against, and take all such action as may be necessary to remove or discharge,
any such Lien.

     3.   Perfection of Security Interest. Borrower agrees to take all actions
requested by Lender and reasonably necessary to perfect, to continue the
perfection of, and to otherwise give notice of, the Lien granted hereunder,
including, but not limited to, execution of financing statements.

D.   Events of Default.

     1.   Definition of Event of Default. The occurrence of any one or more of
the following events shall constitute an "Event of Default" hereunder:

               (i) Borrower's breach of the obligation to pay any amount payable
hereunder on the date that it is due and payable;

               (ii) Borrower's breach of the covenant with respect to the use of
the Advance proceeds;

               (iii) Borrower's commencement of an Insolvency Proceeding, or
Borrower's consent to the commencement of an Insolvency Proceeding or Borrower's
failure to have an Insolvency Proceeding commenced against it dismissed within
ninety (90) days;

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               (iv) the loss, theft, damage or destruction of, or sale (other
than in the ordinary course of business), lease or furnishing under a contract
of service of, any of the Collateral to the extent that such Collateral is not
replaced by like Collateral as covered by insurance or otherwise;

               (v) the creation (whether voluntary or involuntary) of any Lien
upon any of the Collateral, other than the Permitted Liens, or the making or any
levy, seizure or attachment thereof and such Lien, levy, seizure, or attachment
has not been removed, discharged or rescinded within thirty (30) days;

               (vi) the occurrence and continuance of any default under any
lease or agreement for borrowed money that gives the lessor or the creditor of
such indebtedness, as applicable, the right to accelerate the lease payments or
the indebtedness, as applicable, or the right to exercise any rights or remedies
with respect to any of the Collateral; or

               (vii) the entry of any judgment or order against Borrower in
excess of Five Hundred Thousand Dollars ($500,000) which remains unsatisfied or
undischarged and in effect for thirty (30) days after such entry without a stay
of enforcement or execution.

     2.   Rights and Remedies on Event of Default.

          (a) During the continuance of an Event of Default, Lender shall have
the right, itself or through any of its agents, with or without notice to
Borrower (as provided below), as to any or all of the Collateral, by any
available judicial procedure, or without judicial process (provided, however,
that it is in compliance with the UCC), to exercise any and all rights afforded
to a secured party under the UCC or other applicable law. Without limiting the
generality of the foregoing, Lender shall have the right to sell or otherwise
dispose of all or any part of the Collateral, either at public or private sale,
in lots or in bulk, for cash or for credit, with or without warranties or
representations, and upon such terms and conditions, all as Lender, in its sole
discretion, may deem advisable, and it shall have the right to purchase at any
such sale. Borrower agrees that a notice sent at least fifteen (15) days before
the time of any intended public sale or of the time after which any private sale
or other disposition of the Collateral is to be made shall be reasonable notice
of such sale or other disposition. The proceeds of any such sale, or other
Collateral disposition shall be applied, first to the expenses of retaking,
holding, storing, processing and preparing for sale, selling, and the like, and
to Lender's reasonable attorneys' fees and legal expenses, and then to the
Secured Obligations and to the payment of any other amounts required by
applicable law, after which Lender shall account to Borrower for any surplus
proceeds. If, upon the sale or other disposition of the Collateral, the proceeds
thereof are insufficient to pay all amounts to which Lender is legally entitled,
Borrower shall be liable for the deficiency, together with interest thereon at
the Default Rate, and the reasonable fees of any attorneys Lender's employs to
collect such deficiency; provided, however, that the foregoing shall not be
deemed to require Lender to resort to or initiate proceedings against the
Collateral prior to the collection of any such deficiency from Borrower. To the
extent permitted by applicable law, Borrower waives all claims, damages and
demands against Lender arising out of the retention or

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sale or lease of the Collateral or other exercise of Lender's rights and
remedies with respect thereto.

          (b)  To the extent permitted by law, Borrower covenants that it will
not at any time insist upon or plead, or in any manner whatever claim or take
any benefit or advantage of, any stay or extension law now or at any time
hereafter in force, nor claim, take or insist upon any benefit or advantage of
or from any law now or hereafter in force providing for the valuation or
appraisal of the Collateral or any part thereof, prior to any sale or sales
thereof to be made pursuant to any provision herein contained, or the decree,
judgment or order of any court of competent jurisdiction; or, after such sale or
sales, claim or exercise any right under any statute now or hereafter made or
enacted by any state or otherwise to redeem the property so sold or any part
thereof, and, to the full extent legally permitted, hereby expressly waives all
benefit and advantage of any such law or laws, and covenants that it will not
invoke or utilize any such law or laws or otherwise hinder, delay or impede the
execution of any power herein granted and delegated to Lender, but will suffer
and permit the execution of every such power as though no such power, law or
laws had been made or enacted.

          (c)  Any sale, whether under any power of sale hereby given or by
virtue of judicial proceedings, shall operate to divest all Borrower's right,
title, interest, claim and demand whatsoever, either at law or in equity, in and
to the Collateral sold, and shall be a perpetual bar, both at law and in equity,
against Borrower, its successors and assigns, and against all persons and
entities claiming the Collateral sold or any part thereof under, by or through
Borrower, its successors or assigns.

          (d) Borrower appoints Lender, and any officer, employee or agent
of Lender, with full power of substitution, as Borrower's true and lawful
attorney-in-fact, effective as of the date hereof, with power, in its own name
or in the name of Borrower, during the continuance of an Event of Default, to
endorse any notes, checks, drafts, money orders, or other instruments of payment
in respect of the Collateral that may come into Lender's possession, to sign and
endorse any drafts against debtors, assignments, verifications and notices in
connection with accounts, and other documents relating to Collateral; to pay or
discharge taxes or Liens at any time levied or placed on or threatened against
the Collateral; to demand, collect, issue receipt for, compromise, settle and
sue for monies due in respect of the Collateral; to notify persons and entities
obligated with respect to the Collateral to make payments directly to Lender;
and, generally, to do, at Lender's option and at Borrower's expense, at any
time, or from time to time, all acts and things which Lender deems necessary to
protect, preserve and realize upon the Collateral and Lender's security interest
therein to effect the intent of this Note, all as fully and effectually as
Borrower might or could do; and Borrower hereby ratifies all that said attorney
shall lawfully do or cause to be done by virtue hereof. This power of attorney
shall be irrevocable as long as any of the Secured Obligations are outstanding.

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          (e)  All of Lender's rights and remedies with respect to the
Collateral, whether established hereby or by any other agreements, instruments
or documents or by law shall be cumulative and may be exercised singly or
concurrently.

E.   Other Provisions.

     1.   Definitions. As used herein, the following terms shall have the
following meanings:

     "Change of Control" means an event or series of events as a result of which
(i) any person or group, other than a current shareholder of Borrower or a
person or group affiliated with a current shareholder of Borrower, is or becomes
the beneficial owner of shares representing more than fifty percent (50%) of the
combined voting power of the then outstanding securities entitled to vote
generally in elections of Borrower's directors (the "Voting Stock"), (ii)
Borrower consolidates with or merges into any other corporation, or conveys,
transfers or leases all or substantially all of its assets to any person, or any
other corporation merges into Borrower, and, in the case of any such
transaction, Borrower's outstanding common stock is changed or exchanged as a
result, unless the Borrower's shareholders immediately before such transaction
own, directly or indirectly, immediately following such transaction, at least
fifty-one percent (51%) of the combined voting power of the outstanding voting
securities of the corporation resulting from such transaction in substantially
the same proportion as their ownership of the Voting Stock immediately before
such transaction, or (iii) Continuing Directors do not constitute a majority of
the Board of Directors of Borrower (or, if applicable, Borrower's successor).

     "Collateral" means all of Borrower's right, title and interest in each and
all of the Financed Equipment, whether now existing or owned or hereafter
created or acquired by Borrower: and

                    a.   All claims, rights and interests in any of the above
and, all substitutions for, additions and accessions to and proceeds thereof.

     "Continuing Directors" means at any date a member of Borrower's Board of
Directors (i) who was a member of the Board as of the date hereof, or (ii) who
was nominated or elected by at least a majority of the directors who were
Continuing Directors at the time of such nomination or election or whose
election to the Board was recommended or endorsed by at least a majority of the
directors who were Continuing Directors at the time of such nomination or
election.

     "Fiscal Year" means the fiscal year of Borrower.

     "Insolvency Proceeding" means any proceeding commenced by or against
Borrower under any provision of the United States Bankruptcy Code, as amended,
or under any other bankruptcy or insolvency law, including assignments for the
benefit of creditors, formal or

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informal moratoria, compositions, extensions generally with its creditors, or
proceedings seeking reorganization, arrangement or other relief.

     "IPO" means the first sale of Borrower's securities to the public pursuant
to a registration statement under the Securities Act of 1933, as amended, in
which the gross proceeds to Borrower, without reduction for selling commissions
or expenses of the sale equals or exceeds Twenty-Five Million Dollars
($25,000,000).

     "Lien" means any lien (statutory or other), mortgage, pledge,
hypothecation, assignment, deposit arrangement, security interest, charge, claim
or other encumbrance of any kind (including any conditional sale or other title
retention agreement, any lease in the nature thereof, and any agreement to give
any security interest) and any agreement to give or refrain from giving a lien,
mortgage, pledge, hypothecation, assignment, deposit arrangement, security
interest, charge, claim or other encumbrance of any kind.

     "Permitted Liens" means: (i) Liens imposed by law, such as carriers',
warehousemen's, materialmen's and mechanics' liens, or Liens arising out of
judgments or awards against Borrower with respect to which Borrower at the time
shall currently be prosecuting an appeal or proceedings for review; (ii) Liens
for taxes not yet subject to penalties for nonpayment and Liens for taxes the
payment of which is being contested in good faith and by appropriate proceedings
and for which, to the extent required by generally accepted accounting
principles then in effect, proper and adequate book reserves relating thereto
are established by Borrower; and (iii) Liens described in Attachment "B" hereto.

     "UCC" means the Uniform Commercial Code in effect from time to time in the
relevant jurisdiction.

     2.   Governing Law; Venue. This Note shall be governed by the laws of the
State of California, without giving effect to conflicts of law principles.
Borrower and Lender agree that all actions or proceedings arising in connection
with this Note shall be tried and litigated only in the state and federal courts
located in the County of Alameda, State of California or, at Lender's option,
any court in which Lender determines it is necessary or appropriate to initiate
legal or equitable proceedings in order to exercise, preserve, protect or defend
any of its rights and remedies under this Note or otherwise or to exercise,
preserve, protect or defend its Lien, and the priority thereof, against the
Collateral, and which has subject matter jurisdiction over the matter in
controversy. Borrower waives any right it may have to assert the doctrine of
forum non conveniens or to object to such venue, and consents to any court
ordered relief. Borrower waives personal service of process and agrees that a
summons and complaint commencing an action or proceeding in any such court shall
be promptly served and shall confer personal jurisdiction if served by
registered or certified mail to Borrower. If Borrower fails to appear or answer
any summons, complaint, process or papers so served within thirty (30) days
after the mailing or other service thereof, it shall be deemed in default and an
order of judgment may be entered against it as demanded or prayed for in such
summons, complaint, process or papers. The choice of forum set forth herein
shall not be deemed to preclude the enforcement of any judgment

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obtained in such forum, or the taking of any action under this Note to enforce
the same, in any appropriate jurisdiction.

     3.   Notices. Any notice or communication required or desired to be served,
given or delivered hereunder shall be in the form and manner specified below,
and shall be addressed to the party to be notified as follows:

If to Lender:                 Ascend Communications, Inc.
                              1701 Harbor Bay Parkway
                              Alameda, California 94502
                              Attention: Fran Jewels, Esq.
                              Telecopier: (510) 747-2638

If to Borrower:               I3S,Inc.
                              1330 River Bend, Suite 600
                              Dallas, Texas 75242-4953
                              Attention: James Price, President
                              Telecopier: (214) 631-5480

                              With copy to:
                              Matt Hutchins, Vice President, Business
                                                 Development & Corporate Affairs

or to such other address as each party designates to the other by notice in the
manner herein prescribed. Notice shall be deemed given hereunder if (i)
delivered personally or otherwise actually received, (ii) sent by overnight
delivery service, (iii) mailed by first-class United States mail, postage
prepaid, registered or certified, with return receipt requested, or (iv) sent
via telecopy machine with a duplicate signed copy sent on the same day as
provided in clause (ii) above. Notice mailed as provided in clause (iii) above
shall be effective upon the expiration of three (3) business days after its
deposit in the United States mail, and notice telecopied as provided in clause
(iv) above shall be effective upon receipt of such telecopy if the duplicate
signed copy is sent under clause (ii) above. Notice given in any other manner
described in this section shall be effective upon receipt by the addressee
thereof; provided, however, that if any notice is tendered to an addressee and
delivery thereof is refused by such addressee, such notice shall be effective
upon such tender unless expressly set forth in such notice.

     4.   Lender's Rights: Borrower Waivers. To the extent permitted by
applicable law, Lender's acceptance of partial or delinquent payment from
Borrower hereunder, or Lender's failure to exercise any right hereunder, shall
not constitute a waiver of any obligation of Borrower hereunder, or any right of
Lender hereunder, and shall not affect in any way the right to require full
performance at any time thereafter. Except as otherwise specifically provided
herein, and as may be permitted by applicable law, Borrower waives presentment,
diligence, demand of payment, notice, protest and all other demands and notices
in connection with the delivery, acceptance, performance, default or enforcement
of this Note. In any action on this Note, Lender

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need not produce or file the original of this Note, but need only file a
photocopy of this Note certified by Lender be a true and correct copy of this
Note in all material respects.

     5.   Enforcement Costs. Borrower shall pay all costs and expenses,
including, without limitation, reasonable attorneys' fees and expenses Lender
expends or incurs in connection with the enforcement of this Note, the
collection of any sums due hereunder, any actions for declaratory relief in any
way related to this Note, or the protection or preservation of any rights of the
holder hereunder.

     6.   Severability. Whenever possible each provision of this Note shall be
interpreted in such manner as to be effective and valid under applicable law,
but if any provision is prohibited by or invalid under applicable law, it shall
be ineffective to the extent of such prohibition or invalidity, without
invalidating the remainder of the provision or the remaining provisions of this
Note.

     7.   Amendment Provisions. This Note may not be amended or modified, nor
may any of its terms be waived, except by written instruments signed by Borrower
and Lender.

     8.   Binding Effect. This Note shall be binding upon, and shall inure to
the benefit of, Borrower and the holder hereof and their respective successors
and assigns; provided, however, that Borrower's rights and obligations shall not
be assigned or delegated without Lender's prior written consent, given in its
sole discretion, and any purported assignment or delegation without such consent
shall be void ab initio.

     9.   Time of Essence. Time is of the essence of each and every provision of
this Note.

     10.  Headings. Section headings used in this Note have been set forth
herein for convenience of reference only. Unless the contrary is compelled by
the context, everything contained in each section hereof applies equally to this
entire Note.

                                       I3S, INC., a Texas corporation

                                       By: /s/ JIM PRICE
                                          --------------------------------------
                                                      Jim Price
                                                      Chairman & CEO

REVIEWED AND AGREED TO:
ASCEND COMMUNICATIONS,INC.

By: /s/ [ILLEGIBLE]
  ------------------------

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                                 ATTACHMENT "A"
                                       TO
                             SECURED PROMISSORY NOTE
                                       BY
                                    I3S, INC.

                                  BUSINESS PLAN

<PAGE>   12

                                 ATTACHMENT "B"
                                       TO
                             SECURED PROMISSORY NOTE
                                       BY
                                     I3S,INC

                                 PERMITTED LIENS

<PAGE>   13

To:     I3S, Inc. ("I3S")
From:   Lucent Technologies, Inc. InterNetworking Systems ("Lucent")
Date:   8/12/99

Re:  Financing Proposal:
This Preliminary Term Sheet sets forth our current intent with regard to the
financing proposal of Lucent and its subsidiaries in I3S. This Preliminary Term
Sheet is an expression of intent only, does not express the agreement of the
parties and is intended as a negotiation aid by the parties. This Preliminary
Term Sheet shall not constitute a binding agreement of Lucent or I3S, and any
such binding agreement shall be subject to the normal and customary due
diligence by Lucent.

 1.   Credit Line -- It is proposed that Lucent will provide equipment financing
      in the amount of $25,000,000 (which shall include the existing $10,000,000
      equipment financing). The full $25,000,000 shall be made available
      immediately as per the following formula: If, on a quarterly basis, I3S is
      within 50% of the expected revenue and EBITDA projections as outlined in
      its business plan dated March 1999, Lucent will continue to provide
      financing up to the full $25,000,000 amount. If I3S fails to meet the
      stated goals, Lucent reserves the right to suspend or withdraw further
      financing.

 2.   Financing Terms -- Lucent will extend financing in the form of the
      existing Secured Promissory Note dated June 25, 1998 (the "Note"), with
      such Note amended to include:

      a)   An increase the principal amount from $10,000,000 to $25,000,000.
      b)   Interest shall accrue with respect to each Advance at the per annum
           rate equal to Prime at the time each Advance is made.
      c)   All other terms and conditions contained in the Note shall remain
           unchanged.

Both sides recognize that this term sheet is not the definitive agreement. The
terms of this proposal will be set forth in the lease agreement, both parties
will mutually agree upon the terms and provisions of which. If Lucent does not
receive an executed copy of this term sheet by 8/20/99, it shall become null
and void.

Signed and accepted:

/s/ DANIEL A. GILLETT                       /s/ SARAH K. BRYANT
---------------------------------           -----------------------------------
I3S, Inc.                                   Lucent Technologies, Inc.
                                            InterNetworking Systems

Date:  8/20/99                             Date:
     ----------------------------               -------------------------------<PAGE>   1
                                                                   EXHIBIT 10.26

                            OFFICE BUILDING SUBLEASE

          THIS OFFICE BUILDING SUBLEASE (this "SUBLEASE") is dated effective as
of December 16, 1999, and is executed by KERR-McGEE CORPORATION, a Delaware
corporation ("SUBLESSOR"), and THE VIALINK COMPANY, a Delaware corporation
("SUBLESSEE").

1.        RECITALS.

          1.1. Three Galleria Tower Venture, a Texas general partnership
("MASTER LESSOR"), as landlord, and Sublessor's predecessor-in-interest, ORYX
ENERGY COMPANY ("ORYX"), as tenant, entered into a certain First Amended and
Restated Lease Agreement dated as of July 6, 1989, as amended by a First
Amendment to First Amended and Restated Lease Agreement dated as of September 9,
1991 (the "MASTER LEASE"). Oryx assigned all of its right, title and interest in
and to the Master Lease to Sublessor pursuant to an Assignment of Lease dated
February 26, 1999.

          1.2. The premises covered by the Master Lease are more fully
identified in the Master Lease and consist of certain space located in the
office building commonly known as Oryx Energy Center, 13155 Noel Road, Dallas,
Texas (the "BUILDING"), which is located on the real property more particularly
described on EXHIBIT "A-1" attached to the Master Lease.

          1.3. Sublessor desires to sublease to Sublessee, and Sublessee desires
to sublease from Sublessor, the premises identified in Paragraph 2.1, which
constitutes a portion of the "LEASED PREMISES" (as defined in the Master Lease)
covered by the Master Lease, all in accordance with the provisions of this
Sublease.

2.        DEMISE; NET RENTABLE AREA; QUIET ENJOYMENT.

          2.1. Demise. Sublessor subleases to Sublessee, and Sublessee subleases
from Sublessor, in accordance with the provisions of this Sublease, that portion
of the Leased Premises comprised of the entire eighth (8th) floor of the
Building and being stipulated to be 21,716 square feet of "NET RENTABLE AREA"
(as defined in the Master Lease) (the "SUBLEASED PREMISES"), which Subleased
Premises are more particularly described on the floor plans attached hereto as
EXHIBIT "A".

          2.2. Net Rentable Area. Sublessor and Sublessee agree that the actual
number of square feet of Net Rentable Area in the Subleased Premises may be more
or less than the figure stated in Paragraph 2.1; however, for all purposes of
this Sublease, the figure stated in Paragraph 2.1 shall be conclusively deemed
to be the Net Rentable Area of the Subleased Premises.

          2.3. Quiet Enjoyment. Sublessor covenants that Sublessee shall, and
may peacefully have, hold and enjoy the Subleased Premises against any person
whomsoever lawfully claiming the same or any part thereof by, through, or under
Sublessor, but not otherwise, subject to the other provisions

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hereof, provided that Sublessee pays the Rent (as hereinafter defined) and other
sums herein recited to be paid by Sublessee and performs all of Sublessee's
covenants and agreements herein contained.

3.        TERM.

          The term of this Sublease shall begin on the Commencement Date (as
defined below) and end at midnight on October 31, 2001 (the "EXPIRATION DATE").
The "COMMENCEMENT DATE" shall be the earlier of the date upon which Sublessee
first occupies the Subleased Premises or January 15, 2000. Prior to occupying
the Subleased Premises, Sublessee shall execute and deliver to Sublessor a
statement prepared by Sublessor confirming the Commencement Date.

4.        BASE RENT; SECURITY DEPOSIT.

          4.1. Base Rent. During each year of the term of this Sublease,
Sublessee shall pay to Sublessor annual base rent of $325,740.00 (i.e., $15.00
per square foot of Net Rentable Area in the Subleased Premises (the "BASE
RENT").

          4.2. Payment of Base Rent. The annual Base Rent shall be payable in
equal monthly installments equal to 1/12th of the Base Rent. Each installment of
Base Rent shall be due on or before the first day of each month during the term
of this Sublease and shall be paid to Sublessor at its address as set forth in
Paragraph 22.4 (or as later changed pursuant thereto) without notice, demand,
abatement, deduction, diminution, or offset. Monthly installments of Base Rent
shall be prorated for any period during the term hereof which is less than a
full calendar month. The initial installment of Base Rent shall be paid upon the
execution of this Sublease.

          4.3. Security Deposit. Upon the execution of this Sublease, Sublessee
shall deposit with Sublessor a security deposit in the amount of $27,145.00 as
security for the performance of the terms and provisions hereof by Sublessee
(the "SECURITY DEPOSIT"). The Security Deposit or any portion thereof may be
applied to the curing of any default by Sublessee under this Sublease, without
prejudice to any other remedy or remedies which Sublessor may have on account
thereof, and upon such application Sublessee shall pay Sublessor on demand the
amount so applied which shall be added to the Security Deposit. Provided
Sublessee is not then in default under this Sublease, any remaining balance of
the Security Deposit will be returned to Sublessee within thirty (30) days after
the expiration of the term of this Sublease; provided, however, Sublessor shall
have the right to retain and expend all or any portion of the Security Deposit
for cleaning and repairing the Subleased Premises to the extent Sublessee fails
to deliver the Subleased Premises at the termination of this Sublease in a neat
and clean condition and in as good a condition as existed at the date of
possession of same by Sublessee, except for ordinary wear and tear. If Sublessor
assigns its interest in the Subleased Premises during the term hereof, Sublessor
may assign the Security Deposit to the assignee, and thereafter Sublessor shall
have no further liability for the return of the Security Deposit, or any
interest thereon, and Sublessee agrees to look solely to the new sublessor for
the return of the Security Deposit.

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OFFICE BUILDING SUBLEASE              -2-

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5.        ADDITIONAL RENT.

          5.1. Certain Definitions. For purposes hereof: "BASE YEAR" means the
calendar year 2000; "SUBLESSEE'S PERCENTAGE SHARE" means the proportion which
the Net Rentable Area in the Subleased Premises, from time to time, bears to the
total Net Rentable Area in the Leased Premises, from time to time; "TENANT'S
PERCENTAGE SHARE OF OPERATING EXPENSES" has the same meaning given to such term
in the Master Lease; "SUBLESSEE'S PERCENTAGE SHARE OF OPERATING EXPENSES" means
an amount equal to Tenant's Percentage Share of Operating Expenses attributable
to the Subleased Premises during any calendar year of the term of this Sublease;
"SUBLESSEE'S PERCENTAGE SHARE OF EXCESS OPERATING EXPENSES" means the difference
in any calendar year after the Base Year between Sublessee's Percentage Share of
Operating Expenses in that year and Sublessee's Percentage Share of Operating
Expenses in the Base Year.

          5.2. Additional Rent. In addition to Base Rent, Sublessee shall also
pay to Sublessor, during the term of this Sublease, at the same time as Base
Rent is due, an amount equal to Sublessee's Percentage Share of Excess Operating
Expenses. The parties acknowledge that the Master Lease requires Sublessor to
pay on a monthly basis certain estimated costs in order to reimburse Master
Lessor, over the course of each year of the term of the Master Lease, for
Sublessor's share of "OPERATING EXPENSES" (as defined in the Master Lease)
incurred by Master Lessor in owning and operating the "PROJECT" (as defined in
the Master Lease). Sublessee agrees to pay on a monthly basis those estimated
Operating Expenses attributable to Sublessee's Percentage Share of Excess
Operating Expenses. Following the end of each calendar year, a reconciliation is
made against the actual Operating Expenses incurred. Sublessee's obligation to
pay Sublessee's Percentage Share of Excess Operating Expenses, as set forth
above in this Paragraph 5.2, shall be governed by the estimated amounts and
shall be subject to any reconciliation against actual amounts, of such costs and
expenses. Sublessor shall promptly deliver to Sublessee copies of all statements
and notices Sublessor receives from Master Lessor regarding such Operating
Expenses. Items that are specially billed by Master Lessor to Sublessor or
Sublessee, rather than charged generally to office tenants by Master Lessor,
shall be paid by the party requesting the specially billed item in the manner
required by the Master Lease. (The Base Rent together with Sublessee's
Percentage Share of Excess Operating Expenses are hereinafter collectively
referred to as "RENT").

6.        SERVICES; REPAIRS.

          6.1. Provisions of Services. Notwithstanding any other provisions of
this Sublease (including, without limitation, the quiet enjoyment covenant of
Paragraph 2.3), the only facilities, utilities or services (collectively
"SERVICES") to which Sublessee is entitled hereunder are those to which
Sublessor is entitled under the Master Lease. Sublessee shall look solely to
Master Lessor under the Master Lease for all such services, including, without
limitation, the services to be provided by Master Lessor under Section 3.1 of
the Master Lease. Notwithstanding the foregoing, Sublessor does hereby assign,
transfer and set over to Sublessee any and all rights it has or might have
against the Master Lessor under the Master Lease for all such services,
including, without limitation, the services to be provided by Master Lessor
under Section 3.1 of the Master Lease, to the extent that such services involved
are applicable to the Subleased Premises. Sublessee shall pursue any such rights
and remedies by virtue of such assignment at its own cost and expense and shall
indemnify and hold harmless

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OFFICE BUILDING SUBLEASE              -3-

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Sublessor from any loss, cost, claim, damages, expense, causes of action or
liability (including, without limitation, attorneys' fees and costs) asserted
against Sublessor by Master Lessor by reason of Sublessee's pursuit of such
rights and remedies. This assignment will terminate contemporaneously with the
termination of this Sublease.

          6.2. No Abatement or Termination.

                   (a) If Master Lessor shall fail to perform its covenants or
furnish any of the services set forth in the Master Lease (including, without
limitation, the covenants and services set forth in Section 3.1 of the Master
Lease), then Sublessee shall promptly give written notice to Sublessor and to
Master Lessor, specifying in as much detail as possible such failure.

                   (b) Failure by Master Lessor to perform any covenant or
furnish any of the utilities or services set forth in the Master Lease
(including, without limitation, the failure to furnish any of the services
specified in Section 3.1 of the Master Lease) shall not render Sublessor liable
in any respect for damages to either person or property, nor be construed as an
eviction by Sublessor, nor entitle Sublessee to an abatement of Rent (except
that Sublessee may abate Rent and receive reimbursement of out-of-pocket
expenses incurred in temporarily relocating from the Subleased Premises to the
extent that Sublessor would have been entitled under Section 3.1 of the Master
Lease to rental abatement and reimbursement of out-of-pocket relocation expenses
on account of a services interruption to the Subleased Premises had Sublessor
occupied the Subleased Premises at the time of the services interruption), nor
entitle Sublessee to terminate this Sublease in whole or in part (except that
Sublessee may terminate this Sublease if [i] Sublessor has the right to
terminate the Master Lease on account of the services interruption to the
Subleased Premises, but fails to do so, or [ii] a Basic Services Failure [as
defined in the Master Lease] which is not the result of an Unavoidable
Interruption [as defined in the Master Lease] continues for one hundred eighty
(180) consecutive days or more, and such Basic Services Failure affects 25% or
more of the Subleased Premises and it becomes reasonably impracticable for
Sublessee to operate in the Subleased Premises such that Sublessee must relocate
to other premises), nor relieve Sublessee from fulfillment of any covenant or
agreement hereunder, and Sublessee shall have no claim of set-off or rebate of
Rent (except as expressly provided in this Paragraph 6.2) or damages on account
of any interruption in services occasioned thereby or resulting therefrom.

          6.3. Repairs. Sublessee shall maintain the Subleased Premises in the
same or better condition than the condition in which the Subleased Premises
existed on the Commencement Date (reasonable wear and tear excluded).
Notwithstanding any other provisions of this Sublease (including, without
limitation, the quiet enjoyment covenant of Paragraph 2.3), the only repairs and
maintenance to which Sublessee is entitled hereunder are those to which
Sublessor is entitled under the Master Lease. Sublessee shall look solely to
Master Lessor under the Master Lease for all such repairs and maintenance,
including, without limitation, the repairs and maintenance to be provided by
Master Lessor under Section 5.4 of the Master Lease. Sublessor shall have no
obligation to perform or make any such repairs or maintenance with respect to
the Subleased Premises. Sublessee agrees, at its sole cost and expense, to
perform all repairs to and maintenance of the Subleased Premises required by
Sublessor as tenant under the Master Lease, including, without limitation, those
described in Section 5.5 of the Master Lease. Notwithstanding the foregoing,
Sublessor does hereby assign, transfer and set over to Sublessee any and all
rights it has or might have against the Master Lessor under the Master Lease for
all repairs

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OFFICE BUILDING SUBLEASE              -4-

<PAGE>   5

and maintenance to be provided by Master Lessor under Section 5.4 of the Master
Lease, to the extent that such repairs involved are applicable to the Subleased
Premises. Sublessee shall pursue any such rights and remedies by virtue of such
assignment at its own cost and expense and shall indemnify and hold harmless
Sublessor from any loss, cost, claim, damages, expense, cause of action or
liability (including, without limitation, attorneys' fees and costs) asserted
against Sublessor by Master Lessor by reason of Sublessee's pursuit of such
rights and remedies. This assignment will terminate contemporaneously with the
termination of this Sublease.

7.        USE OF SUBLEASED PREMISES.

          The Subleased Premises shall be used by Sublessee solely as business
offices.

8.        INCORPORATION OF MASTER LEASE.

          8.1. Compliance with Master Lease. Except (i) to the extent that the
provisions of the Master Lease are in clear conflict with the terms and
provisions of this Sublease, and (ii) as expressly otherwise provided in this
Sublease (including, without limitation, Paragraph 17 hereof), Sublessee shall
comply with all of the provisions of the Master Lease that are to be observed or
performed during the term hereof by Sublessor as tenant thereunder with respect
to the Subleased Premises. Notwithstanding any other provision of this Sublease,
Sublessee shall not, by any act or omission, cause Sublessor to be in violation
of or in default under the Master Lease.

          8.2. Incorporation of Master Lease.

                   (a) Insofar as the provisions of the Master Lease pertaining
to the Subleased Premises do not conflict with specific provisions hereof or are
not specifically excluded by Paragraph 17 hereof, such provisions are
incorporated by this reference into this Sublease as fully as if completely
restated herein. Subject to the preceding sentence, Sublessee shall be bound by
all the provisions of the Master Lease pertaining to the Subleased Premises and
shall perform all of the obligations and responsibilities that Sublessor is
obligated to perform pursuant to the Master Lease pertaining to the Subleased
Premises. Therefore, for the purposes of this Sublease, wherever in the Master
Lease the word "LANDLORD" is used, it shall mean Sublessor and wherever in the
Master Lease the word "TENANT" is used, it shall mean Sublessee and wherever in
the Master Lease the word "LEASED PREMISES" or similar words are used, they
shall mean the Subleased Premises; all terms not specifically defined herein
shall have the same meanings designated thereto in the Master Lease provided
that the same is not in conflict with the terms and provisions of this Sublease.

                  (b) Notwithstanding Paragraph 8.2(a), this Sublease shall not
and does not create any rights in Master Lessor or any third parties.

          8.3. Subleased Premises. The parties acknowledge and agree that
Sublessee's rights and obligations hereunder relate to only those portions of
the Leased Premises covered by the Master Lease that are a part of, or are
related or appurtenant to, the Subleased Premises.

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OFFICE BUILDING SUBLEASE              -5-

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          8.4. Subject to Master Lease. This Sublease is expressly subject to
and inferior to the Master Lease, and no provision of this Sublease shall be
construed in a manner that would violate the terms of the Master Lease.

          8.5. Approval of Master Lease. Sublessee represents that it has read,
is familiar with and approves all of the provisions of the Master Lease to the
extent that such provisions relate to the Subleased Premises.

9.        LIMITATION OF LIABILITY AND INDEMNITY.

          9.1. Condition of Property. Notwithstanding any provision of this
Sublease or the Master Lease to the contrary, Sublessor shall not be liable to
Sublessee or any of its officers, directors, shareholders, agents, employees,
servants, or invitees for any death or injury to any person or persons or for
damage to property due to the conduct of Sublessee's business in the Subleased
Premises, the condition or design of or any defect in the Subleased Premises,
the Building, the Project, or any part or component thereof (including, without
limitation, any mechanical, electrical, plumbing, heating, air conditioning or
other systems or equipment), which may exist or subsequently occur, except to
the extent of any gross negligence or willful misconduct of Sublessor or its
agents, employees, contractors, licensees or invitees, but such exception shall
be subject to the waiver of liability provisions and waiver of subrogation
provisions of Sections 6.6 and 6.7 of the Master Lease, which are incorporated
herein pursuant to Paragraph 8 hereof.

          9.2. Default by Master Lessor. Sublessor shall not be responsible or
liable for any violation or default by Master Lessor under the Master Lease
(including, without limitation, the failure to provide services or repairs) or
for the acts or omissions of any tenant of the Building, the Project, or any
other third party.

10.       CONDEMNATION; CASUALTY.

          10.1. Condemnation. The provisions of Section 6.1 of the Master Lease
(regarding condemnation) are hereby modified only in that (i) Sublessor shall
have no obligation whatsoever to restore the Subleased Premises and no liability
in connection therewith, and (ii) Sublessor shall be entitled to all
condemnation proceeds except that Sublessee shall be entitled to receive any
condemnation proceeds to the extent expressly and directly awarded to Sublessee
by the condemning authority.

          10.2. Casualty.

                  (a) In the event of a fire or other casualty in the Subleased
Premises, Sublessee shall immediately give written notice thereof to Sublessor
and to Master Lessor.

                  (b) If the Subleased Premises shall be partially destroyed by
fire or other casualty so as to render the Subleased Premises untenantable, in
whole or in part, and if the Master Lease is not terminated as therein provided,
then the Rent shall abate thereafter as to the portion of the Subleased Premises
rendered untenantable to the extent that the rent payable under the Master Lease
is abated as a result of such casualty, until such time as Master Lessor has
restored the Subleased Premises to permit

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OFFICE BUILDING SUBLEASE              -6-

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Sublessee's re-occupancy of the Subleased Premises. Sublessee shall pay all
costs with respect to any such restoration of the Subleased Premises that are
required to be paid by Sublessor to Master Lessor under the Master Lease.

                  (c) In the event of damage or destruction to the Subleased
Premises, the Leased Premises, the Building or the Project, or any portions
thereof, and the Master Lease is terminated as therein provided, then all
accrued and unpaid Rent for the period prior to such destruction shall be paid
by Sublessee and thenceforth this Sublease and the obligations of the parties
hereunder shall cease and come to an end, except for any continuing obligations
the parties may have to each other (including, without limitation, liability
under any indemnities provided for in this Sublease).

                  (d) The parties acknowledge and agree that Sublessor shall
have no obligation or liability in connection with any such damage or any
reconstruction of the Subleased Premises.

11.       CURRENT LEASEHOLD IMPROVEMENTS; "AS-IS, WHERE-IS" CONDITION.

          Sublessee accepts the Subleased Premises in their "AS-IS, WHERE-IS"
condition. The taking possession of the Subleased Premises by Sublessee shall be
conclusive evidence as against Sublessee that the Subleased Premises were in the
condition agreed upon between Sublessor and Sublessee. Sublessor and Sublessee
expressly agree that there are and shall be no implied or express warranties of
merchantability, habitability, suitability, fitness for a particular purpose or
any other kind arising out of this Sublease, and there are no warranties,
whether written, oral, express or implied, which extend beyond those expressly
set forth in this Sublease.

12.       ALTERATIONS, ADDITIONS AND IMPROVEMENTS.

          12.1. Consent. Sublessee shall not make any alterations, additions or
improvements to the Subleased Premises without first obtaining the written
consent of Sublessor (which consent shall not be unreasonably withheld) and the
consent of Master Lessor. Any alterations, additions and improvements will be of
a quality substantially equivalent to or better than the quality of improvements
within the Subleased Premises as of the Commencement Date. Sublessee shall
procure any and all insurance required by Sublessor and Master Lessor to be
maintained during the construction of the alterations, additions and
improvements. Construction of any alterations, additions or improvements shall
be performed by a general construction contractor approved by Master Lessor and
Sublessor. As between and among Master Lessor, Sublessor and Sublessee,
Sublessee hereby assumes any and all liability for any and all injuries to or
death of, any and all persons (including, without limitation, Sublessee's
contractors and subcontractors and employees), and any liability for any and all
damage to property caused by, or resulting from, or arising out of any act or
omission of Sublessee, Sublessee's contractors and their subcontractors or
employees in the performance of the alterations, additions and improvements.
Sublessee further agrees to defend, indemnify and save harmless Sublessor and
Master Lessor from and against all damages, costs, liability, losses and
expenses (including reasonable legal fees and expenses) that Sublessor or Master
Lessor may incur, suffer or pay as a result of claims or lawsuits due to,
because of, or arising out of any and all such injuries, death and/or damage,
except to the extent caused by the gross negligence or willful misconduct of
Sublessor or Master Lessor, as applicable, or their respective agents,
employees, contractors, licensees or invitees.

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          12.2. Sublessor's Property. All such alterations, additions,
improvements shall be made at Sublessee's expense and shall become Sublessor's
property, and shall remain on and be surrendered with the Subleased Premises at
the termination of this Sublease without disturbance, molestation, or injury.
All such work shall comply with all legal requirements and with the terms and
provisions of the Master Lease. Nothing contained in this Sublease shall prevent
Sublessee from removing all furniture, furnishings and trade fixtures owned by
Sublessee and used in its business, provided they can be removed without damage
to the Subleased Premises. Sublessee shall repair any damage to the Subleased
Premises and the Building caused by such removal.

13.       INSURANCE.

          Sublessor shall not be obligated to obtain or maintain any insurance
with respect to the Subleased Premises. Sublessee shall obtain and maintain in
force all insurance required under the Master Lease pertaining to the Subleased
Premises including, but not limited to, broad form commercial or comprehensive
general liability insurance including a cross-liability provision with limits,
as of the date of this Sublease, of not less than $2,000,000.00 for bodily
injury or damage to or destruction of property for any one occurrence (it being
acknowledged that the insurance limits are subject to change in accordance with
Section 6.5 of the Master Lease) with an insurance company or companies
authorized to do business in the State of Texas and with and A.M. Best Company,
Inc. rating of B+ or better. If such insurance is written on a claims-made form,
it must provide for (i) a retroactive date prior to, or coincident with, the
date of this Sublease, and (ii) a minimum extended claims reporting period of
one year. In addition, Sublessee shall name Sublessor and Master Lessor as
additional insured under any such insurance policy. Sublessee shall cause all
insurance policies to contain waiver of subrogation provisions acceptable to
Sublessor and Master Lessor. Sublessee agrees that certificates of insurance or
certified copies of such insurance policies will be delivered to Sublessor and
Master Lessor within ten (10) days following the execution of this Sublease. All
policies shall contain an endorsement requiring thirty (30) days prior written
notice from any insurer to Sublessor and Master Lessor before any change,
cancellation, termination, or reduction in or of such policies. All policies
shall acknowledge that they provide primary coverage with respect to the
additional insureds thereunder and that such policies as are separately
maintained by the additional insureds shall be excess insurance.

14.       NO ASSIGNMENT OR SUB-SUBLEASE WITHOUT CONSENT.

          Sublessee may not sell, assign, transfer, convey, or encumber this
Sublease or any part thereof or any interest therein or relet the Subleased
Premises, in whole or in part (hereinafter referred to as a "TRANSFER"), without
first obtaining the written consent of Sublessor. Any attempted Transfer in
violation hereof shall be null and void. Any Transfer by Sublessee shall not
relieve Sublessee from any liability or obligation created by this Sublease. If
Sublessor elects to consent to a Transfer (which consent may be granted or
withheld in Sublessor's sole and absolute discretion), and if the Rent due and
payable by a transferee under any such permitted Transfer (or a combination of
the Rent payable thereunder plus any bonus or other consideration therefor or
incident thereto) in respect of the interval in question exceeds the Rent due
under this Sublease allocable to the portion of the Subleased Premises covered
thereby for the same interval, such excess shall belong to Sublessor. Sublessee
shall hold all

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amounts it receives which are payable to Sublessor in trust and shall deliver
such amounts to Sublessor within ten days after Sublessee's receipt thereof.

15.       DEFAULT.

          15.1. Default by Sublessee. Each of the following shall constitute an
"EVENT OF DEFAULT" by Sublessee under this Sublease: (i) if default shall be
made in the payment of any sum of Rent, or of any sum other than Rent, to be
paid by Sublessee to Sublessor under this Sublease and such failure to pay
continues for a period of five (5) days after written notice thereof has been
given by Sublessor to Sublessee (provided, however, Sublessor shall not be
required to provide such notice more than once in any twelve (12) month period,
the second such failure constituting an Event of Default without Sublessor
providing such notice); or (ii) if default shall be made in the performance of
any of the other covenants and conditions which Sublessee is required to observe
and perform under this Sublease and such default continues for a period of
thirty (30) days after written notice thereof has been given by Sublessor to
Sublessee; or (iii) if the interest of Sublessee under this Sublease shall be
levied on under execution or other legal process; or (iv) if any petition shall
be filed by or against Sublessee to declare Sublessee a bankrupt or to delay,
reduce or modify Sublessee's debts or obligations; or (v) if Sublessee is
declared insolvent according to law or if any assignment of Sublessee's property
shall be made for the benefit of creditors or if a receiver or trustee is
appointed for Sublessee or its property; or (vi) if Sublessee shall default
under any of the terms and provisions of the Master Lease which, by the terms of
this Sublease, are applicable hereto; then Sublessor may treat the occurrence of
any one or more of the foregoing events as a breach of this Sublease and
thereupon, at Sublessor's option, Sublessor shall have any one or more of the
following described remedies, in addition to all other rights and remedies
provided at law or in equity:

                  (a) Sublessor may terminate this Sublease and repossess the
          Subleased Premises and be entitled to recover as damages a sum of
          money equal to the total of (i) the cost of recovering the Subleased
          Premises, (ii) the accrued and unpaid Rent at the time of termination,
          plus interest thereon at the maximum lawful per annum rate under the
          laws of the State of Texas from the due date, (iii) the present value
          [discounted at the rate of eight percent per annum] of the balance of
          all Rent for the remainder of the Sublease term less the present value
          (discounted at the same rate) of the fair market rental value of the
          Subleased Premises for the same period (but only to the extent the
          remainder is a positive number) and (iv) any other sum of money and
          damages including any attorney's fees and court costs owed by
          Sublessee to Sublessor.

                  (b) Sublessor may terminate Sublessee's right of possession
          (but not this Sublease) and may repossess the Subleased Premises by
          forcible entry or detainer suit or otherwise, without demand or notice
          of any kind to Sublessee and without terminating this Sublease, in
          which event Sublessor may, but shall be under no obligation to do so,
          relet the Subleased Premises for the account of Sublessee for such
          Rent and upon such terms as shall be satisfactory to Sublessor. For
          the purpose of such reletting, Sublessor is authorized to decorate
          and/or to make any repairs, changes, alterations and/or additions in
          or to the Subleased Premises that may be reasonably necessary to
          restore the Subleased Premises to a "BUILDING STANDARD" (as defined in
          the Master Lease) condition. In addition, (i) if Sublessor shall fail
          to relet the Subleased Premises, then Sublessee shall pay to Sublessor
          as damages a sum equal to the amount of all

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<PAGE>   10

         accrued and unpaid Rent and other accrued and unpaid sums provided for
         in this Sublease; or (ii) if the Subleased Premises are relet and a
         sufficient sum shall not be realized from such reletting after paying
         the accrued and unpaid Rent and other accrued and unpaid sums due
         hereunder at the time of reletting, the cost of recovering possession
         and of collecting rent accruing under such subletting, and all of the
         costs and expenses reasonably incurred in making such decorations,
         repairs, changes, alterations and/or additions necessary to relet the
         Subleased Premises (plus interest on all of the same at the maximum
         lawful contract rate), then Sublessee shall satisfy and pay any such
         deficiency upon demand therefor from time to time. Sublessee agrees
         that Sublessor may file suit to recover any sums falling due under the
         terms of this Paragraph 15.1(b) from time to time, and that no delivery
         to or recovery by Sublessor of any sum due Sublessor hereunder shall be
         any defense in any action to recover any amount of money not
         theretofore reduced to judgment in favor of Sublessor, nor shall such
         reletting be construed as an election on the part of Sublessor to
         terminate this Sublease unless a written notice of such intention is
         given to Sublessee by Sublessor. Notwithstanding any such reletting
         without termination, Sublessor may at any time thereafter elect to
         terminate this Sublease for such previous breach.

                  (c) Sublessor may enter the Subleased Premises and cure at
         Sublessee's expense any default.

                  (d) Sublessor may, but shall not be required to, use, apply or
         retain all or any part of the Security Deposit for the payment of any
         Rent or any other sum in default, or for the payment of any other
         amount which Sublessor may spend or become obligated to spend by reason
         of Sublessee's default, or to compensate Sublessor for any other loss
         or damage which Sublessor may suffer by reason of Sublessee's default,
         including, without limitation, costs and attorneys' fees incurred by
         Sublessor to recover possession of the Subleased Premises. If any
         portion of the Security Deposit is so used or applied, Sublessee shall,
         upon demand, deposit cash with Sublessor in an amount sufficient to
         restore the Security Deposit to its original amount, and Sublessee's
         failure to do so shall constitute a default hereunder by Sublessee.

         15.2. Limited Duty to Mitigate. If Sublessor expels or removes
Sublessee from the Subleased Premises without terminating or forfeiting this
Sublease or accepting surrender of the Subleased Premises, Sublessor must
attempt to mitigate its damages. In any situation in which Sublessor is
attempting to mitigate its damages, Sublessor will conclusively be deemed to
have done so if Sublessor lists the Subleased Premises with a real estate broker
or agent and considers all written proposals for such space made by such broker
or agent; provided, however, that in no event will Sublessor (a) be obligated to
travel outside a radius of thirty (30) miles from the Subleased Premises in
order to meet with a prospective tenant, (b) be obligated to expend monies for
finish-out requested by a prospective tenant unless Sublessor, in its sole
discretion, believes that the excess rent Sublessor will receive and the credit
of the prospective tenant supports such a decision, (c) be required to give
preference to the Subleased Premises over other spaces in the Leased Premises,
(d) be required to agree to allow an existing tenant of the Project or subtenant
of the Leased Premises to move from their existing space to all or any of the
Subleased Premises, or (e) be required to accept any lease proposal which it, in
its sole discretion, deems unacceptable.

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OFFICE BUILDING SUBLEASE              -10-

<PAGE>   11
          15.3. Default by Sublessor. Except where the provisions of this
Sublease grant Sublessee an express, exclusive remedy, or deny Sublessee a
remedy, if Sublessor should fail to perform or observe any covenant, term,
provision or condition of this Sublease and such default should continue beyond
a period of thirty (30) days (or such longer period as is reasonably necessary
to remedy such default, provided Sublessor shall continuously and diligently
pursue such remedy at all times until such default is cured) following notice
thereof by Sublessee to Sublessor, then Sublessee shall have as its sole and
exclusive remedy the right to commence such actions at law or in equity to which
Sublessee may be entitled, including without limitation any action for specific
performance or damages but expressly excluding an action to declare a
termination of this Sublease. The rights of Sublessee pursuant to this Paragraph
15.3 shall be subject to any express provisions of this Sublease providing for
remedies different from, or in exclusion of, the remedies above-described. In no
event shall Sublessor be liable to Sublessee for consequential or special
damages by reason of a failure to perform (or default) by Sublessor or Master
Lessor hereunder or otherwise. Sublessee shall have the right, but not the
obligation to cure any default by Sublessor under the Master Lease and be
reimbursed by Sublessor for the actual amounts expended to cure any such default
upon demand from Sublessee.

          15.4. Non-Waiver. Failure of either party to declare any default
immediately upon occurrence thereof, or delay in taking any action in connection
therewith, shall not waive such default or right to take such action, but such
party shall have the right to declare any such default or take such action at
any time. Sublessor's acceptance of partial payment of any sum owing hereunder
shall not constitute a waiver of or be deemed to constitute a waiver or estoppel
by Sublessor of the right to collect the full amount of any sum owing hereunder.

          15.5. Cumulative Remedies. All rights and remedies of Sublessor
enumerated in this Sublease (including, without limitation, indemnification
rights) shall be cumulative and shall not exclude any other right or remedy
allowed by law or in equity. These rights and remedies may be exercised or
enforced concurrently and as often as necessary.

          15.6. Sublessor's Default and Sublessee's Remedy. Sublessor shall be
deemed to be in default under this Sublease if Sublessor shall fail to comply
with any term, provision, or covenant of this Sublease and shall not cure such
failure within thirty (30) days after receipt of written notice thereof from
Sublessee, or in the event such failure to comply cannot reasonably be cured
within thirty (30) days, Sublessor fails to commence cure within thirty (30)
days and pursue to a diligent conclusion. In the event Sublessor is in default
under this Sublease, Sublessee may terminate this Sublease by giving Sublessor
written notice and this Sublease shall terminate and be void as of the date
given in such notice. In the event of such cancellation, this Sublease shall be
of no further force and effect, and neither party shall have any rights or
obligations hereunder.

16.       EXCULPATION.

          Sublessee shall maintain the Subleased Premises in the same or better
condition than the condition in which the Subleased Premises existed on the
Commencement Date (reasonable wear and tear excluded). Sublessee acknowledges
and agrees that Sublessor shall not be responsible for any maintenance,
services, or repairs to the Subleased Premises, to the Building, the Project, or
any part thereof, nor shall Sublessor be liable for any interruption in
utilities or services to the Subleased

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OFFICE BUILDING SUBLEASE              -11-

<PAGE>   12

Premises, nor for loss or damage to any person or any property of Sublessee or
its employees or invitees by theft or otherwise, nor shall Sublessor be liable
for any damage or disturbance caused by other tenants of the Building or the
Project. Any and all covenants, undertakings and agreements herein made on the
part of Sublessor are made and intended not as personal covenants,
understandings and agreements for the purpose of binding Sublessor personally or
the assets of Sublessor, except only Sublessor's interest in the leasehold under
the Master Lease; and Sublessee specifically agrees to look solely to
Sublessor's (or its successors') leasehold interest under the Master Lease for
the recovery of any judgment from Sublessor (or its successors) relating to this
Sublease, it being agreed that Sublessor and its successors (and their
directors, officers, employees and agents) shall never be personally liable for
any such judgment.

17.       INAPPLICABILITY OF CERTAIN PROVISIONS OF MASTER LEASE.

          The Master Lease contains certain provisions that are not applicable
to this Sublease. The parties agree that the following sections of the Master
Lease are not incorporated herein and do not form a part of this Sublease:

          Any provisions that are superseded by or in direct conflict with the
          provisions hereof; any provisions relating to Master Lessor's or
          Sublessor's obligations regarding the initial construction of the
          Building, the Project, or the Leased Premises by Master Lessor,
          including any rights of Sublessor to approve matters in connection
          therewith, the intent of this provision being to acknowledge that
          construction of the Building, the Project and the Leased Premises
          covered by the Master Lease are complete; Section 1.1 (Leased
          Premises); Section 1.2 (Term); Section 1.3 (Base Building Design);
          Section 1.4 (Use); Section 2.1 (Rental Payments); Section 2.2 (Base
          Rental); Section 2.5 (Cash Inducements); Section 2.6 (Refurbishment
          Allowance); Section 2.7 (Additional Inducements); Section 2.8
          (Agreements Inducement); the provisions of Section 3.1 (Services) that
          would otherwise require Sublessor to provide services as stated
          therein (it being acknowledged that Sublessee agrees to look solely to
          Master Lessor for any such services in accordance with Paragraph 6
          hereof); the provisions of Section 3.2 (Keys and Locks) that would
          require Sublessor to pay for any keys and/or access cards for
          Sublessee; Section 3.3 (Graphics and Building Directory); Section 3.4
          (Parking) (it being acknowledged that the parking provision set forth
          in Paragraph 19 hereof shall govern this Sublease); Section 3.5
          (Building Identity and Signs); Section 3.6 (Communications Equipment);
          the provisions of Section 4.4 (Laws and Regulations; Rules of
          Building) that would otherwise require Sublessor to act on behalf of
          the Master Lessor; Section 5.1 (Base Building Improvements); Section
          5.2 (Leasehold Improvements); Section 5.3 (Holdover and Related
          Costs); the provisions of Section 5.4 (Repairs by Landlord) that would
          otherwise require Sublessor to make any repairs or perform any
          maintenance, repair, refurbishing or replacement (it being
          acknowledged that Sublessee agrees to look solely to Master Lessor for
          any such items in accordance with Paragraph 6 hereof); the provisions
          of Section 5.7 (Management) that would otherwise give Sublessee the
          right to approve or select the Project manager; the provisions of
          Sections 6.1, 6.3, 6.4, and 6.5 (Condemnation, Casualty Clause,
          Casualty Insurance, and Liability Insurance) that would otherwise
          require Sublessor to provide and maintain insurance on the Subleased
          Premises or to repair or restore the Subleased Premises in the event
          of a casualty or a condemnation (it being acknowledged that Sublessee
          agrees to look solely to

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OFFICE BUILDING SUBLEASE              -12-

<PAGE>   13

          Master Lessor for such items in accordance with Paragraph 10 hereof);
          Section 6.6 (Hold Harmless and Indemnity) (it being acknowledged that
          the indemnity provisions set forth in Paragraph 9 hereof shall govern
          this Sublease); Section 7.1 (Default and Remedies) (it being
          acknowledged that the default provisions set forth in Paragraph 15
          hereof shall govern this Sublease); Section 7.3 (Negation of Lien for
          Rent); Section 7.7 (Holding Over); the provisions of Section 7.8
          (Subordination) that would otherwise require Sublessor to act on
          behalf of the Master Lessor with respect to any mortgage or deed of
          trust placed on the Project; Section 7.10 (Vacating the Leased
          Premises); Section 7.11 (Tenant Net Worth); Section 8.1 (Sublease or
          Assignment by Tenant); Section 8.2 (Assignment by Landlord) (it being
          acknowledged that Sublessor has unrestricted rights to assign its
          interest in this Sublease); Section 8.5 (Memorandum of Lease); Section
          8.6 (Consents); Section 8.7 (Publicity); Article IX (Options); Section
          10.2 (Fair Market Rental); Section 11.1 (Notices) (it being
          acknowledged that notices required under this Sublease shall be
          delivered as set forth in Paragraph 22.4 hereof); Section II
          (Brokers); the defined terms in Section 11.4 (Other Definitions) to
          the extent they do not relate to Master Lease provisions which are
          incorporated herein by reference; Section 11.8 (Extension of Lease I);
          the exhibits attached to the Master Lease to the extent they do not
          relate to Master Lease provisions which are incorporated herein by
          reference. Except as provided in the following sentence, Section 2.3
          of the Master Lease is incorporated herein by reference for all
          purposes except for determining (i) the Base Year, and (ii) the
          fraction used for calculating Sublessee's Percentage Share of
          Operating Expenses, both of which shall be governed by Paragraph 5 of
          this Sublease. For purposes of determining Sublessee's Percentage
          Share of Operating Expenses, Sublessor shall be entitled to rely upon
          any and all statements and certifications furnished to Sublessor by
          Master Lessor and Master Lessor's accountants and representatives, and
          Sublessor shall not be liable to Sublessee for any errors or
          inconsistencies contained in any such statements or certifications.

          Sublessee's obligations under Paragraph 8 hereof and elsewhere to
comply with or conform to the provisions of the Master Lease do not extend to
any provisions of the Master Lease that are not incorporated herein and do not
form a part of this Sublease as stated in this Paragraph 17, but nevertheless
Sublessee shall not by any act or failure to act cause any default to exist
under the Master Lease.

18.       ACCEPTANCE OF BUILDING AND SUBLEASED PREMISES.

          Sublessee, by taking possession of the Subleased Premises,
acknowledges and agrees that it: (a) accepts the Subleased Premises as suitable
for the purposes for which they are leased; (b) accepts the Subleased Premises
as being in a good and satisfactory condition; (c) accepts the Subleased
Premises subject to the Master Lease and all applicable laws, agreements,
covenants, restrictions and matters of record; and (d) waives any defects in the
Subleased Premises, except to the extent that Master Lessor is obligated to
maintain and/or repair the same pursuant to the Master Lease.

19.       PARKING.

          During the term of this Sublease, Sublessee shall have the right to
use three (3) parking spaces for every 1,000 square feet of Net Rentable Area in
the Subleased Premises, which parking spaces shall

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OFFICE BUILDING SUBLEASE              -13-

<PAGE>   14

be located in the parking garages for Two Galleria Tower or Three Galleria Tower
(collectively, the "GALLERIA GARAGES"). The parking spaces shall be unreserved
spaces located in portions of the Galleria Garages designated by and under the
control of Master Lessor. Sublessee's use of the spaces in the Galleria Garages
are subject to all restrictions in the Master Lease. Sublessee understands that
any such spaces which are designated by Master Lessor in the Two Galleria Tower
garage after the commencement of the Sublease are subject to being transferred
by Master Lessor to the Three Galleria Tower garage upon seven (7) days notice
thereof to Sublessee. The parking spaces shall be provided to Sublessee at no
charge. Sublessee shall have no parking rights under this Sublease or the Master
Lease, except as expressly set forth herein.

20.       HAZARDOUS MATERIALS.

          Sublessee shall not cause or permit any Hazardous Materials (as such
term is defined in the Master Lease) to be used, stored, generated, released or
disposed of on or in the Subleased Premises, Building or Project by Sublessee,
Sublessee's agents, employees, contractors, or invitees except to the extent
consistent with customary and reasonable office business practices and provided
(a) such Hazardous Materials do not endanger the health of any person on or
about the Subleased Premises or the Project, and (b) Sublessee complies with all
Legal Requirements applicable to such Hazardous Materials. In the event of a
release of any Hazardous Material, Sublessee, in addition to complying with all
applicable law concerning such release, shall notify Sublessor immediately upon
becoming aware of the same and take such measures as required under all
applicable law and consistent with such law, including, for example, the removal
or causing the removal and appropriate disposition of such Hazardous Materials,
all at Sublessee's expense. If Sublessee breaches or violates any provision in
this Paragraph 20, or if the Subleased Premises, Building or Project becomes
contaminated in any manner by reason of the fault of Sublessee, its agents,
employees, contractors or invitees, Sublessee shall indemnify, defend and hold
Sublessor harmless from any and all claims, damages, fines, judgments,
penalties, costs, liabilities, or losses arising as a result thereof.

21.       AMERICANS WITH DISABILITIES ACT.

          Sublessee, at its sole expense, will be responsible for causing the
design and construction of any alterations and improvements hereafter made to
the Subleased Premises to be in compliance with the Americans with Disabilities
Act of 1990 (the "ADA"). Sublessee further agrees to be responsible for any ADA
mandated changes to pre-existing conditions in the Subleased Premises which are
required due to the fact that Sublessee is altering or improving the Subleased
Premises. Sublessee agrees to indemnify and hold harmless Sublessor for the
above described obligations.

22.       LEASE OF EXISTING FURNITURE.

                   (a) Terms of Furniture Lease. In addition to the Subleased
Premises, Sublessor also hereby leases to Sublessee, and Sublessee hereby leases
from Sublessor, a portion of the furniture presently situated in the Subleased
Premises (the "EXISTING FURNITURE"). The exact description and quantities of the
Existing Furniture being leased will be determined in the manner described in
Paragraph 22(c) below. The Existing Furniture is hereby leased on the same terms
and conditions as

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OFFICE BUILDING SUBLEASE              -14-

<PAGE>   15

provided in this Sublease for the subleasing of the Subleased Premises, except
that: (a) on the Expiration Date, Sublessee shall return the Existing Furniture
to Sublessor in the same or better condition than the condition in which the
Existing Furniture existed on the date on which this Sublease was executed,
normal wear and tear excepted; and (b) the monthly rental for the Existing
Furniture shall be 1/12th of the product of the number of square feet of Net
Rentable Area in the Subleased Premises times $1.00 (i.e., $1,809.66) (the
"FURNITURE RENT").

                      (b) Payment of Furniture Rent. Each installment of
Furniture Rent shall be due on or before the first day of each month during the
term of this Sublease and shall be paid to Sublessor at its address as set forth
in Paragraph 23.4 (or as later changed pursuant thereto) without notice, demand,
abatement, deduction, diminution, or offset. Monthly installments of Furniture
Rent shall be prorated for any period during the term hereof which is less than
a full calendar month. The initial installment of Furniture Rent shall be paid
upon the Commencement Date.

                      (c) Furniture Inventory. On or before the Commencement
Date, Sublessor and Sublessee will prepare an inventory confirming the type,
amount and condition of the Existing Furniture. Sublessee acknowledges that it
will have thoroughly inspected the Existing Furniture as of the Commencement
Date, and that except as agreed by Sublessor and Sublessee in writing as an
attachment to the Existing Furniture inventory, the Existing Furniture will be
deemed to have been delivered to Sublessee in a good condition as of such date.
Sublessee shall also be entitled to use the Additional Furniture (herein so
called) more particularly described on EXHIBIT "C" attached hereto and made a
part hereof for all purposes; provided, however, Sublessee shall be responsible
for moving the Additional Furniture from its current location to the Subleased
Premises at Sublessee's sole cost and expense.

23.          MISCELLANEOUS PROVISIONS.

             23.1. Attorneys' Fees. If any action at law, in equity or in
arbitration, including an action for declaratory relief, is brought to enforce
or interpret the provisions of this Sublease, the prevailing party shall be
entitled to recover attorneys' fees and court (or arbitration) costs from the
other party.

             23.2. Applicable Law. This Sublease shall be construed, enforced
and governed by the laws of the State of Texas. Venue for any action involving
this Sublease shall be in Dallas County, Texas.

             23.3. Surrender of Premises and Keys. Sublessee shall, at the
expiration of this Sublease, quietly and peaceably surrender the Subleased
Premises without the requirement of notice to Sublessee, and Sublessee will
deliver to Sublessor all keys to the Subleased Premises. At the time of such
surrender, the Subleased Premises shall be in the same or better condition than
the condition in which the Subleased Premises existed on the Commencement Date
(reasonable wear and tear excluded).

             23.4. Notices. Any notices, requests, instructions or other
communications to Sublessor or Sublessee required or permitted to be given under
this Sublease must be in writing and shall be deemed given if (a) personally
delivered to the address for Sublessor or Sublessee stated below, (b) sent by
United States Mail, prepaid, certified or registered, return receipt requested,
to such address, or (c) delivered by overnight express delivery service to such
address. Any notice which is delivered personally

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OFFICE BUILDING SUBLEASE              -15-

<PAGE>   16

or sent by overnight express in the manner provided herein shall be deemed to
have been duly given to the party to whom it is directed upon actual receipt by
such party. Any notice addressed and mailed in the manner herein provided shall
be deemed to have been given to the party to whom it is addressed at the close
of business, local time, of the recipient on the third regular business day
following the date of deposit of such item in a depository of the United States
Postal Service.

          The address for Sublessor shall be:

          KERR-McGEE CORPORATION
          123 Robert S. Kerr Avenue
          Oklahoma City, Oklahoma 73102
          Attention:  Manager, Real Estate Operations

          The address for Sublessee shall be:          [STAMP]

          THE VIALINK COMPANY
          13155 Noel Road, Suite 800
          Dallas, Texas 75240-5090
          Attention:  David Lloyd
                      Vice President - Operations

Either party shall have the right to change its address to which notices shall
be sent by giving the other notice thereof as required by this Paragraph 23.4.

         23.5. Rules and Regulations. Sublessee shall comply with all rules and
regulations now or hereafter promulgated by Master Lessor and/or Sublessor
pertaining to the Subleased Premises, the Building, the Project or the Parking
Facility. Attached hereto as EXHIBIT "B" are the current Building rules and
regulations promulgated by Sublessor. As used in EXHIBIT "B", the term "Lessor"
shall mean and refer to Master Lessor and/or Sublessor, and the term "Tenant"
shall mean and refer to Sublessee.

         23.6. Financial Statements. Sublessee shall, no later than one hundred
twenty (120) days after the end of each fiscal year, deliver to Sublessor copies
of Sublessee's balance sheet and statement of profit and loss for the preceding
fiscal year, each prepared in accordance with generally accepted accounting
principles, such financial statements to be audited by a nationally or
regionally recognized accounting firm.

         23.7. Authority. Sublessee hereby represents to Sublessor that the
person signing on behalf of Sublessee has the power and authority to bind
Sublessee to this Sublease; and Sublessor hereby represents to Sublessee that
the person signing on behalf of Sublessor has the power and authority to bind
Sublessor to this Sublease.

         23.8. Paragraph Headings, Gender, etc. The paragraph headings in this
Sublease are not intended to be used in construing the substance of this
Sublease. Unless the context of this Sublease otherwise requires (a) words of
any gender are deemed to include the other gender, (b) words using the singular
or plural number also include the plural or singular number, respectively, (c)
the terms

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OFFICE BUILDING SUBLEASE              -16-

<PAGE>   17

"hereof", "herein", "hereby", "hereto", and derivative or similar words refer
to this entire Sublease, (d) the term "Section" or "Article" refers to the
specified section or article of the Master Lease, (e) the term "Paragraph"
refers to the specified Paragraph of this Sublease, and (f) all references to
"dollars" or "$" refer to currency of the United States of America.

          23.9. Late Charge. If any installment of Rent or any other sum which
becomes owing by Sublessee to Sublessor under the provisions hereof is not
received by Sublessor by the due date therefor, Sublessee, to the extent
permitted by law, agrees to pay, in addition to such installment of Rent or such
other sum owed, interest on such installment of Rent or such other sums owed at
the rate of five percentage points over the Prime Rate (as defined in the Master
Lease) or the highest rate permitted by applicable law, whichever is lower,
until paid. It is understood that the late payment charge shall be for the
purpose of reimbursing Sublessor for the additional costs and expenses which
Sublessor presently expects to incur in connection with the handling and
processing of late installment payments of Rent and other sums owed. Any amounts
paid by Sublessor to cure any defaults of Sublessee hereunder, which Sublessor
shall have the right but not the obligation to so cure, shall, if not repaid by
Sublessee within five days of demand by Sublessor, thereafter bear interest at
the rate of five percentage points over the Prime Rate or the highest rate
permitted by applicable usury law, whichever is lower, until paid.

          23.10. Consent of Master Lessor. If Sublessor determines that the
consent of Master Lessor is required for this Sublease, then this Sublease shall
not be effective unless and until such consent is obtained.

          23.11. Obligations of Sublessor. It is understood and agreed that any
and all covenants or obligations of Sublessor contained in this Sublease shall
be binding upon Sublessor and its successors and assigns only with respect to
breaches occurring or accruing during its and their respective ownership of the
Sublessor's interest hereunder.

          23.12. Rules of Construction. The terms and provisions of this
Sublease shall not be construed against or in favor of a party hereto merely
because such party is the "Sublessor" or the "Sublessee" hereunder or such party
or its counsel is the draftsman of this Sublease.

          23.13. Confidentiality of Master Lease. Sublessee acknowledges and
agrees that the terms and provisions of the Master Lease are confidential, and
Sublessee agrees to not disclose the terms and provisions of the Master Lease to
any person other than Sublessee's affiliates, employees, partners, attorneys,
architects, or other consultants (and only to the foregoing persons on a "need
to know" basis).

          23.14. Lien for Rent. To secure the payment of all Rent due and to
become due hereunder, and the faithful performance of all of the other covenants
of this Sublease required by Sublessee to be performed, Sublessee hereby gives
to Sublessor an express contractual lien on, and security interest in and to,
all property, chattels and merchandise owned by Sublessee which may be placed in
the Subleased Premises.

          23.15. Holding Over. If Sublessee should remain in possession of the
Subleased Premises after the expiration or termination of this Sublease, without
the execution by Sublessor and Sublessee of a

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OFFICE BUILDING SUBLEASE              -17-

<PAGE>   18

new sublease, then Sublessee shall be deemed to be occupying the Subleased
Premises as a tenant-at-sufferance subject to all the covenants and obligations
of this Sublease, and Sublessee shall pay as Rent per month for the entire
holdover period 150% the Rent payable hereunder for the month preceding the
commencement of such holding over, calculated on a daily basis. No holding over
by Sublessee after the term of this Sublease, either with or without the consent
and acquiescence of Sublessor, shall operate to extend the Sublease for a longer
period than one month, and any holding over with the consent of Sublessor in
writing shall thereafter constitute this Sublease a sublease from month to month
at a Rent rate as agreed to in writing by Sublessor and Sublessee.

          23.16. Brokers. Sublessor and Sublessee warrant and represent to each
other that no real estate broker or salesman has been involved by either party
in this Sublease other than Sublessor's agent, The Staubach Company, and
Sublessee's agent, Kennedy Wilson Brokerage Services; and each party agrees
to indemnify and hold the other party harmless from and against any and all
claims of any other real estate broker or salesman due to acts of such party or
such party's representatives.

          23.17. Prior Agreements Superseded. This Sublease constitutes the sole
agreement of the parties and supersedes any prior understandings or written or
oral agreement between the parties respecting the subject matter hereof.

          23.18. Time of Essence. Time is of the essence in this Sublease.

          23.19. Binding on Successors. Sublessor shall have the right to
transfer and assign, in whole or in part, all its rights and obligations
hereunder and in the Master Lease, and upon any such assignment, this Sublease
shall be binding upon and inure to the benefit of the successors and assigns of
Sublessor, and shall be binding upon and inure to the benefit of Sublessee, its
successors, and, to the extent assignment may be approved by Sublessor
hereunder, Sublessee's assigns.

          23.20. Counterparts. This Sublease may be executed concurrently in one
or more counterparts, each of which shall be deemed an original, but all of
which together shall constitute one and the same instrument.

          23.21. Amendments. This Sublease may not be altered, changed or
amended, except by an instrument in writing executed by Sublessor and Sublessee.

          23.22. Exhibits. The terms and provisions of any exhibits attached
hereto are hereby incorporated herein and made a part hereof for all purposes.

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

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OFFICE BUILDING SUBLEASE              -18-

<PAGE>   19

          EXECUTED by Sublessor on the ___ day of December, 1999 to be
effective as of the day and year first above written.

                                   SUBLESSOR:

                                   KERR-McGEE CORPORATION,
                                   a Delaware corporation

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

          EXECUTED by Sublessee on the ___ day of December, 1999, to be
effective as of the day and year first above written.

                                   SUBLESSEE:

                                   THE VIALINK COMPANY,
                                   a Delaware corporation

                                   By:  /s/ J. ANDREW KERNER
                                        ----------------------------------------
                                        Name: J. ANDREW KERNER
                                              ----------------------------------
                                        Title: VP Finance
                                               ---------------------------------

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OFFICE BUILDING SUBLEASE              -19-

<PAGE>   20

                                   EXHIBIT "A"

                        FLOOR PLAN OF SUBLEASED PREMISES

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OFFICE BUILDING SUBLEASE              -20-

<PAGE>   21

                                   EXHIBIT "B"

                         SUBLESSOR RULES AND REGULATIONS

1.       Sidewalks, doorways, vestibules, halls, stairways, and other similar
         areas shall not be obstructed by Sublessee or used for any purpose
         other than ingress and egress to and from the Subleased Premises and
         for going from one part of the Building to another part of the
         Building.

2.       Plumbing fixtures and appliances shall be used only for the purpose for
         which designated, and no sweeping, rubbish, rags or other unsuitable
         material shall be thrown or placed therein. Damage resulting to any
         fixtures or appliances from misuse by Sublessee shall be at its
         expense, and Sublessor shall not in any case be responsible therefore.

3.       No signs, advertisements, or notices shall be painted or affixed on or
         to any window or doors or other part of the Building except of such
         color, size, and style and in such places as shall be first approved in
         writing by Sublessor. No nails, hooks or screws shall be driven or
         inserted in any part of the Building except with the express consent of
         Sublessor.

4.       Sublessor will provide and maintain a directory for all sublessees to
         be located in the lobby of the Building; no other directory shall be
         permitted unless previously consented to by Sublessor in writing. All
         directory listings will be at Sublessee's expense.

5.       Sublessor shall provide, at Sublessee's expense, all locks for doors in
         the Subleased Premises. Sublessee shall not place any additional lock
         or locks on any door in its Subleased Premises without Sublessor's
         written consent. All requests for duplicate keys shall be made to the
         Property Manager and will be furnished at Sublessee's expense.

6.       Proposed plans for alterations affecting floors, walls, woodwork, trim,
         windows, ceilings, equipment, and/or any other physical portion of the
         Building must be approved in writing by Sublessor. Sublessee will refer
         all contractors, contractor's representatives and installation
         technicians tendering any service to Sublessee to Sublessor for
         Sublessor's supervision, approval and control before the performance of
         any contractual services. This provision shall apply to all work
         performed in the Building, including, but not limited to, installations
         of telephones, telegraph equipment, electrical devices and attachments,
         and any and all installations of every nature affecting floors, walls,
         woodwork, trim, windows, ceilings, equipment and any other physical
         portion of the Building.

7.       Movement in or out of the Building of furniture or office equipment, or
         dispatch or receipt by Sublessee of any bulky material, merchandise or
         materials which requires use of elevators or stairways or movement
         through the Building entrances or lobby shall be restricted to such
         hours as Sublessor shall designate. All such movement shall be under
         the supervision of Sublessor and in the manner agreed between Sublessee
         and Sublessor by prearrangement before performance. Such prearrangement
         initiated by Sublessee shall include determination by Sublessor, and

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OFFICE BUILDING SUBLEASE              -21-

<PAGE>   22

         subject to its decision and control, as to the time, method, and
         routing of movement and as to limitations for safety or other concern
         which may prohibit any article, equipment, or any other item from being
         brought into the Building. Sublessee assumes all risks as to the damage
         to articles moved and injury to persons or public engaged or not
         engaged in such movement, including equipment, property, and personnel
         of Sublessor if damaged or injured as a result of an act in connection
         with carrying out this service for Sublessee; and Sublessor shall not
         be liable for acts of any persons engaged in or any damage or loss to
         any of said property or persons resulting from any act in connection
         with such service performed for Sublessee.

8.       Sublessor reserves the right in its sole discretion to prescribe the
         weight and position of safes and other heavy equipment, which shall in
         all cases stand on supporting devices approved by Sublessor. All
         damages done to the Building by taking in or putting out any property
         of Sublessee, or done by Sublessee's property while in the Building,
         shall be repaired at the expense of Sublessee.

9.       Sublessee shall notify the Property Manager when safes or other heavy
         equipment are to be taken in or out of the Building, and the moving
         shall be done under the supervision of the Property Manager, after
         receiving written permission from Sublessor. Persons employed to move
         such property must be acceptable to Sublessor.

10.      Should Sublessee require telegraphic, telephonic, annunciator or other
         communications service, Sublessor will direct electricians where and
         how wires are to be introduced and placed and none shall be introduced
         or placed except as Sublessor shall direct.

11.      Corridor doors, when not in use, shall be kept closed. Stairwell doors
         shall remain closed at all times.

12.      Sublessee shall cooperate with Sublessor's employees in keeping its
         Subleased Premises neat and clean. Unless Sublessee is responsible for
         cleaning its own space pursuant to its Office Building Sublease,
         Sublessee shall not employ any person for the purpose of such cleaning
         other than the Building cleaning and maintenance personnel.

13.      Sublessor shall be in no way responsible to Sublessee, its agents,
         employees, or invitees for any loss of property from the Subleased
         Premises or public areas or for any damages to any property thereon
         from any cause whatsoever.

14.      Sublessee shall not make or permit any improper noises in the Building
         or otherwise interfere in any way with other tenants and subtenants or
         persons having business with them.

15.      Nothing shall be swept or thrown into the corridors, halls, elevator
         shafts or stairways. No birds or animals shall be brought into or kept
         in, on or about the Subleased Premises (except for Seeing Eye dogs).

16.      No vending machines of any type shall be allowed in the Subleased
         Premises without the prior written consent of Sublessor.

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OFFICE BUILDING SUBLEASE              -22-

<PAGE>   23

17.      No machinery of any kind shall be operated by Sublessee in the
         Subleased Premises without prior written consent of Sublessor, nor
         shall Sublessee use, or keep, in the Building any flammable or
         explosive fluid or substance.

18.      No portion of the Subleased Premises shall at any time be used as
         sleeping or lodging quarters.

19.      Sublessee is requested to lock all doors leading to corridors and to
         turn out all lights at the close of its working day.

20.      Sublessor shall not be responsible for lost or stolen personal
         property, money or jewelry from the Subleased Premises or public areas
         regardless of whether such loss occurs when area is locked against
         entry or not.

21.      Sublessee shall not tamper with or attempt to adjust temperature
         control thermostats in the Subleased Premises. Sublessor shall make, or
         cause Master Lessor to make, adjustments in thermostats on call from
         Sublessee.

22.      Sublessee will comply with all requirements necessary for the security
         of the Subleased Premises, including the use of service passes issued
         by Sublessor or Master Lessor for after hours removal of office
         furniture/packages, and use of security control cards for after hours
         entry.

23.      All window blinds are to remain down and tilted at a 45 degree angle
         toward the street to help maintain comfortable room temperatures and to
         conserve energy.

24.      All routine deliveries to the Subleased Premises from 8:00 a.m. to 5:00
         p.m. weekdays shall be made through the freight elevator. Advanced
         arrangements should be made through the Management Office for large
         deliveries and moves. Large deliveries need to be scheduled for between
         3:00 p.m. and 5:00 p.m. weekdays. Move-in and move-outs need to be
         scheduled for after 6:00 p.m. weekdays, and all day Saturdays and
         Sundays. Passenger elevators are to be used only for the movement of
         persons, unless an exception is approved by the Building Management
         Office.

25.      All requests for overtime air conditioning and/or heating must be
         submitted to the Management Office in writing by 4:30 p.m.

26.      All requests for keys, locks or graphics must be submitted in writing
         to the Management Office.

27.      Solicitation of any kind is strictly forbidden unless approved in
         advance by the Management Office.

28.      It is strongly recommended by the Dallas Fire Department that an A, B,
         C Multi-Purpose type fire extinguisher be kept in the Subleased
         Premises in an accessible location.

29.      Sublessor reserves the right to rescind any of these rules and
         regulations and to make such other and further rules and regulations as
         in its judgment shall, from time to time, be needed for the

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OFFICE BUILDING SUBLEASE              -23-

<PAGE>   24

         safety, protection, care and cleanliness of the building, the operation
         thereof, the preservation of good order therein and the protection and
         comfort of the subtenants and tenants and their guests, employees and
         invitees, which rules and regulations, when made and written notice
         thereof is given to a subtenant or tenant; shall be binding upon it in
         like manner as if originally herein prescribed.

30.      A No Smoking Policy is in effect in Oryx Energy Center. Smoking is
         prohibited in the common areas, restrooms, lobbies and elevators of the
         Building. It shall be the responsibility of Sublessee to develop a
         Smoking Policy within its Subleased Premises.

31.      No firearms (hand guns, rifles, shot guns, etc.) or cases for carrying
         firearms (regardless whether or not any such case actually contains a
         firearm) shall be introduced to, or allowed in, the Subleased Premises,
         the Building, the Project or the Parking Facility.

32.      Parking regulations include a two hour visitor parking limitation with
         temporary parking access cards available from security. All employees
         must park in designated areas behind the gates.

33.      City of Dallas recycling program must be followed by all tenants to
         meet the City of Dallas regulations.

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OFFICE BUILDING SUBLEASE              -24-

<PAGE>   25

                                   EXHIBIT "C"

                        INVENTORY OF ADDITIONAL FURNITURE

1.      Four (4) work stations.
2.      Thirteen (13) drafting tables.
3.      Thirteen (13) chairs.
4.      Five (5) file cabinets.

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OFFICE BUILDING SUBLEASE              -25-

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