MERCATOR SOFTWARE, INC.

August 1, 2003

David Linthicum
[address]

Dear Mr. Linthicum:

                  This is an agreement ("Agreement") that has been reached with
you in connection with your continued employment with Mercator Software, Inc.
(the "Company"). Capitalized terms not defined herein shall have the meanings
given thereto in that certain Agreement and Plan of Merger (the "Merger
Agreement"), dated as of August 1, 2003, by and among Ascential Software
Corporation, a Delaware corporation ("Ascential"), Greek Acquisition
Corporation, a Delaware corporation and wholly owned subsidiary of Ascential,
and the Company.

                  1.       You and the Company agree that you will continue to
                           remain employed by the Company from the date hereof
                           until the end of the sixty (60) day period following
                           the consummation of the currently contemplated tender
                           offer to be undertaken by Ascential ("Offer"). During
                           such period you agree to perform to the best of your
                           abilities such reasonable duties and responsibilities
                           as may be assigned to you by the Board of Directors
                           of the Company or its designee.

                  2.       During such period you shall continue to receive
                           salary from the Company in accordance with the
                           Company's regular payroll practices at the rate
                           currently in effect and shall be entitled to employee
                           benefits substantially comparable to those presently
                           being provided to you.

                  3.       Following the consummation of the Offer, you shall,
                           at the written request of the Company or Ascential,
                           resign from any and all positions you hold as an
                           officer or director of the Company, or any of its
                           respective parents, subsidiaries and affiliates, at
                           any level.

                  4.       From and after the date which is sixty (60) days
                           following the consummation of the Offer, either you,
                           by voluntary resignation, or the Company may
                           terminate your employment at any time and for any
                           reason (in each case a "termination"), and upon such
                           termination you shall execute a release in the form
                           set forth as Exhibit A hereto, and you shall receive
                           the severance and change of control benefits that are
                           payable pursuant to the Company's Change of Control
                           Benefits Plan (the "Plan") all as set forth in
                           Exhibit B attached hereto (assuming termination on
                           September 30,



                           2003). Nothing contained herein shall be construed as
                           a waiver of any rights which you may have under any
                           such agreement or the Plan or an amendment of such
                           Plan or agreement, provided, however, that (i) you
                           acknowledge that, except with respect to your death
                           or disability, any such severance benefits shall be
                           contingent upon your remaining employed with the
                           Company during such sixty (60) day period, and (ii)
                           the amount of any severance payments due to you under
                           the provisions of the Plan or agreement shall,
                           notwithstanding anything to the contrary contained
                           the Plan or agreement, be paid to you in the manner
                           set forth on Exhibit B (assuming termination on
                           September 30, 2003) following the date upon which
                           your employment is terminated. Notwithstanding clause
                           (i) of the preceding sentence, in the event that the
                           Company terminates your employment, other than for
                           Cause (as defined below) during such period, you
                           shall immediately be eligible for the benefits
                           pursuant to and in accordance with the Plan, which
                           shall be subject to the schedule set forth in clause
                           (ii) of the preceding sentence, in addition to the
                           remaining amounts due and owing to you with respect
                           to the balance of the 60 day period. For purposes
                           hereof, Cause is defined as your commission of an
                           intentional malicious act, other than an act
                           performed at the Company's request, that causes
                           material and substantial harm to the Company.

                  5.       EXHIBIT B contains a statement of the amount and
                           payment terms of your benefits assuming you are
                           terminated effective September 30, 2003. The amounts
                           are subject to adjustment depending on the actual
                           date of termination in accordance with the terms and
                           conditions of the Plan. The terms and conditions of
                           the payments of such amounts will be governed by this
                           agreement and the Plan.

                  6        In the event the Offer is not consummated, this
                           Agreement shall be null and void and of no force or
                           effect.



                  If the above sets forth our agreement as you understand it and
consent to it, please so signify by executing the enclosed copy of this letter
and return it to me at the address listed above.

         Mercator Software, Inc.

          /s/ Roy C. King
         -------------------------
         Name: Roy C. King
         Title: Chairman and CEO

Agreed to and Accepted:

          /s/ David Linthicum
         -------------------------
         Name: David Linthicum