<PAGE>

                                                                   EXHIBIT 10.15

                                   AMENDMENT
                                      TO
                              EMPLOYMENT AGREEMENT

        This Amendment to Employment Agreement is entered into as of March
28, 2000 (this "Amendment"), between ObjectSpace, Inc., a Delaware
corporation (the "Company"), and Mr. David Norris, an individual residing in
the State of Texas ("Mr. Norris") and amends that certain Employment
Agreement between the parties dated as of December 30, 1998 (the "Agreement")

        In consideration of the mutual promises contained in this Amendment,
the parties agree as follows:

        1. As consideration for this Amendment, the Company agrees to, and
           will provide updated confidential and proprietary information and
           trade secrets to Mr. Norris during his term of employment and after
           the execution of this Amendment

        2. Section 8(a) of the Agreement is hereby amended in its entirety to
           read as follows:

           (a) Non-Compete.  During the period that the Executive is employed
               by the Employer and for a period of one year following the
               termination of employment for any reason, the Executive agrees
               that the Executive will not (i) own or have any interest in,
               or act as a manager, officer, director, executive, consultant,
               agent or representative of, or assist in any way or in any
               capacity, any person, firm, association, partnership,
               corporation, limited liability company, or other entity that
               (a) manufactures, distributes or sells products in competition
               with the Employer's Products (as hereinafter defined),
               anywhere within North America, or (b) solicit business in
               competition with the Employer from (y) any of the Employer's
               customers who transacted business with the Employer during the
               one year period prior to such termination with whom the
               Executive or his direct reports had contact, or (z) any of the
               Employer's potential customers with whom the Employer or his
               direct reports had contact during the one year period prior to
               such termination.  As used herein, "Products" means the same
               or similar products or services as the Employer provides
               during Executive's term of employment, including, but not
               limited to a line of "middleware" products known as "Voyager,"
               business to business integration products known as
               "OpenBusiness," and object-oriented consulting and training
               services.  The Executive acknowledges and agrees that the
               Employer sells the Products throughout North America and,

<PAGE>

                                                                   EXHIBIT 10.15

               therefore, the geographic scope of the restriction contained
               herein is both reasonable and necessary under the
               circumstances.  Notwithstanding anything in this Section 8(a)
               to the contrary, in the event employment is terminated by
               Employer without Cause or by Executive for Good Reason,
               Executive shall be entitled to provide training and consulting
               services to any Persons other than customers and potential
               customers identified in clause (b)(y) and (b)(z) of this
               Section 8(a).

        3. Except as set forth herein, all other terms and conditions of the
Agreement remain in full force and effect, and are hereby ratified.

The parties have signed this Amendment as of the date first above set forth.

OBJECTSPACE, INC.


By: /s/ Paul A. Lipari               /s/ David Norris
    ---------------------------      ---------------------------
        Paul A. Lipari                   David Norris
        Chief Financial Officer


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