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                             [LOGO OF NEURON DATA]

                                                                   EXHIBIT 10.16

                                             April 12, 1999

William G. Seawick
11270 Page Mill Road
Los Altos Hills, CA 94022

Dear Bill:


Neuron Data, Inc. (the "Company") is very pleased to extend this offer of
employment to you to serve as the Company's Vice President, Marketing, reporting
to me. We believe that you will be a tremendous addition to the Neuron Data team
and we are all very excited about the prospect of you joining us. The terms and
conditions of your employment, should you decide to accept our offer, are as
follows:

 .    Compensation: Your annual rate of base salary will be $155,000, payable in
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     accordance with the Company's standard payroll practice for salaried
     employees. This salary will be subject to adjustment at my discretion each
     subsequent year as part of the review of your compensation.

 .    Bonus: You will be eligible to receive an annual incentive bonus of up to
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     thirty percent (30%) of your annual salary compensation. Bonus amounts, if
     any, would be payable based upon your 100% achievement of corporate and
     individual performance objectives as determined in the Company's sole
     discretion.

 .    Stock Options: Following the commencement of your employment, we will
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     recommend to the Board of Directors that you receive an "incentive stock
     option" of 240,000 shares of the Company's common stock at an exercise
     price per share equal to the fair market value of the Company's common
     stock on the date the option is granted, and in accordance with the
     Company's Stock Option Plan and Stock Option Agreement. In the event of
     change of control of the Company, vesting will accelerate to the extent of
     50% of the unvested portion of the option on the closing date of the change
     of control, subject to a minimum aggregate vesting of two-thirds of the
     option.

 .    Benefits: During your employment, Neuron Data will provide you and your
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     eligible dependents with health benefits in accordance with the Company's
     health plan (summary attached). You will be entitled to time off in the
     amount of ten vacation days, increasing after three years per the Company
     policy, three personal days, and designated national holidays.

 .    Proprietary Information and Inventions Agreements: You will be required, as
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     a condition to your employment with the Company, to enter into the
     Company's standard Employee Proprietary Information Agreement. Please have
     this completed by your first day of employment.

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 .  Period of Employment: All employment with the Company is "at will", meaning
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   that either you or the Company will be entitled to terminate your employment
   with the Company, with or without cause, at any time. You understand and
   agree that only the Company President can enter into an agreement on any
   other terms and he or she can only do so in writing signed by him or her and
   you.

 .  Severance: Should your employment with the Company be terminated
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   involuntarily for other than cause or change of control, the Company will pay
   you severance in four monthly installments, the total amount equal to (i)
   four months salary payable at the rate of the annual base salary in effect
   for you at the time of such termination plus (ii) the amount of the bonus
   prorated for such four month period at the target rate in effect on the
   effective date of such termination, subject to agreements of non-compete and
   hiring restrictions. In addition, the Company will provide benefits
   continuation if needed for the four month period. Such payments will be made
   monthly for a period of four months or until you take a position with another
   company, whichever is sooner.

   Should your employment with the Company be terminated involuntarily for other
   than cause subsequent to a change of control, the Company will pay you
   severance in six monthly installments, the total amount equal to (i) six
   months salary payable at the rate of the annual base salary in effect for you
   at the time of such termination plus (ii) the amount of the bonus prorated
   for such six month period at the target rate in effect on the effective date
   of such termination, subject to agreements of non-compete and hiring
   restrictions. In addition, the Company will provide benefits continuation if
   needed for the six month period. Such payments will be made monthly for a
   period of six months or until you take a position with another company,
   whichever is sooner.

 .  Arbitration: Except with respect to matters for which injunctive relief is
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   sought pending arbitration under California law, all questions, disputes,
   and/or controversies that may arise out of or in connection with this
   agreement, arbitration shall be conducted in Mountain View, California, in
   accordance with the rules of the American Arbitration Association. Each party
   hereto shall select one arbitrator and the two arbitrators shall jointly
   select a third arbitrator. Each party agrees that the arbitrators may not
   award punitive damages for or against either party. The decision of a
   majority of the arbitrators shall be final and binding upon both parties, who
   hereby agree to comply therewith.

 .  In addition to the matters set forth above, the Company has personnel
   policies relating to the other terms and conditions of employment at the
   Company, and that though the Company may change these policies from time to
   time at its sole discretion, the voluntary "at will" nature of your
   employment will not be changed.
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We hope that you find the foregoing terms acceptable, and we look forward to
your response to this offer. You may indicate your acceptance of employment by
signing and dating the enclosed duplicate original of this letter and returning
it to me by Thursday, April 15th. We believe that in your role as the Company's
Vice President, Marketing you will make a significant contribution to the
Company's future success, and we look forward to welcoming you to the Neuron
Data Team.


                                             Very truly yours,

                                             /s/ Thomas F. Kelly

                                             Thomas F. Kelly
                                             President & CEO


AGREED TO AND ACCEPTED BY:

/s/ William G. Seawick                         4-12-99
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William G. Seawick                           Date