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                                                                Exhibit 10.16.4


                             TANTAU SOFTWARE, INC.

                                1999 STOCK PLAN


     1. PURPOSE OF THE PLAN.  The purposes of this Stock Plan are to attract
and retain the best available personnel for positions of substantial
responsibility, to provide additional  incentive to Employees,  Directors and
Consultants and to promote the success of the Company's  business.  Options
granted under the Plan may be Incentive Stock Options or Nonstatutory  Stock
Options,  as determined by the  Administrator  at the time of  grant.  Stock
Purchase  Rights  may also be granted under the plan.

2.  DEFINITIONS. As used herein, the following definitions shall apply:

          (a)  "ADMINISTRATOR"  means the Board or any of its  Committees as
shall be administering the Plan in accordance with Section 4 hereof.

          (b)  "APPLICABLE LAWS" means the requirements relating to the
administration of stock option plans under U.S. state corporate laws, U.S.
federal and state securities laws, the Code, any stock exchange or quotation
system on which the Common Stock is listed or quoted and the applicable laws
of any other country or jurisdiction where Options or Stock Purchase Rights
are or will be granted under the Plan.

          (c) "BOARD" means the Board of Directors of the Company.

          (d) "CODE" means the internal Revenue Code of 1986, as amended.

          (e) "COMMITTEE" means a committee of Directors appointed by the
Board in accordance with Section 4 hereof.

          (f) "COMMON STOCK" means the Common Stock, par value $.001 per
share, of the Company.

          (g) "COMPANY" means Tantau Software, Inc., a Delaware corporation.

          (h) "CONSULTANT" means any person who is engaged by the Company or
any Parent or Subsidiary to render consulting or advisory services to such
entity.

          (i) "DIRECTOR" means a member of the Board of Directors of the
Company.

          (j) "DISABILITY" means total and permanent disability as defined in
Section 22(e)(3) of the Code.

          (k) "EMPLOYEE" means any person, including Officers and Directors,
employed by the Company or any Parent or Subsidiary of the Company. A service
Provider shall not cease to be an Employee in the case of (i) any leave of
absence approved by the Company or (ii) transfers between locations of the
Company or between the Company, its Parent, any Subsidiary, or any successor. A
leave of absence approved by the Company shall include sick leave, military


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leave, or any other leave of absence approved by an authorized representative of
the Company. For purposes of Incentive Stock Options, no such leave may exceed
ninety days, unless reemployment upon expiration of such leave is guaranteed by
statute or contract, including Company policies. If reemployment upon expiration
of a leave of absence approved by the Company is not so guaranteed, on the 181st
day of such leave any Incentive Stock Option held by the Optionee shall cease to
be treated as an Incentive Stock Option and shall be treated for tax purposes as
a Nonstatutory Stock Option. Neither service as a Director nor payment of a
director's fee by the Company shall be sufficient to constitute "employment" by
the Company.

          (l) "EXCHANGE ACT" means the Securities Exchange Act of 1934, as
amended.

          (m) "FAIR MARKET VALUE" means, as of any date, the value of Common
Stock determined as follows:

              (i) If the Common Stock is listed on any established stock
exchange or a national market system, including without limitation the Nasdaq
National Market of The Nasdaq SmallCap Market of The Nasdaq Stock Market, its
Fair Market Value shall be the closing sales price for such stock (or the
closing bid, if no sales were reported) as quoted on such exchange or system
for the last market trading day prior to the time of determination, as
reported in THE WALL STREET JOURNAL or such other source as the Administrator
deems reliable;

             (ii) If the Common Stock is regularly quoted by a recognized
securities dealer but selling prices are not reported, its Fair Market Value
shall be the mean between the high bid and low asked prices for the Common
Stock on the last market trading day prior to the day of determination; or

             (iii) In the absence of an established market for the Common
Stock, the Fair Market Value thereof shall be determined in good faith by the
Administrator.

          (n) "INCENTIVE STOCK OPTION" means an Option intended to qualify as an
incentive stock option within the meaning of Section 422 of the Code.

          (o) "NONSTATUTORY STOCK OPTION" means an Option not intended to
qualify as an Incentive Stock Option.

          (p) "OFFICER" means a person who is an officer of the Company within
the meaning of Section 16 of the Exchange Act and the rules and regulations
promulgated thereunder.

          (q) "OPTION" means a stock option granted pursuant to the Plan.

          (r) "Option Agreement" means a written or electronic agreement
between the Company and an Optionee evidencing the terms and conditions of an
individual Option grant. The Option Agreement is subject to the terms and
conditions of the Plan.

          (s) "OPTION EXCHANGE PROGRAM" means a program whereby outstanding
Options are exchanged for Options with a lower exercise price.

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          (t) "OPTIONED STOCK" means the Common Stock subject to an option or
a Stock Purchase Right.

          (u) "OPTIONEE" means the holder of an outstanding Option or Stock
Purchase Right grated under the Plan.

          (v) "PARENT" means a "parent corporation," whether now or hereafter
existing, as defined in Section 424(e) of the Code.

          (w) "PLAN" means this 1999 Stock Plan.

          (x) "RESTRICTED STOCK" means shares of Common Stock acquired pursuant
to a grant of a Stock Purchase Right under Section 11 below.

          (y) "SERVICE PROVIDER" means an Employee, Director or Consultant.

          (z) "SHARE" means a share of the Common Stock, as adjusted in
accordance with Section 12 below.

          (aa) "STOCK PURCHASE RIGHT" means a right to purchase Common Stock
pursuant to Section 11 below.

          (bb) "SUBSIDIARY" means a "subsidiary corporation," whether now or
hereafter existing, as defined in Section 424(f) of the Code.

     3. STOCK SUBJECT TO THE PLAN. Subject to the provisions of Section 12 of
the Plan, the maximum aggregate number of Shares that may be subject to option
and sold under the Plan is 5,325,000 Shares. The Shares may be authorized but
unissued, or reacquired Common Stock.

     If an Option or Stock Purchase Right expires or becomes
unexercisable without having been exercised in full, or is surrendered pursuant
to an Option Exchange Program, the unpurchased Shares which were subject thereto
shall become available for future grant or sale under the Plan (unless the Plan
has terminated). However, Shares that have actually been issued under the Plan,
upon exercise of either an Option or Stock Purchase Right, shall not be returned
to the Plan and shall not become available for future distribution under the
Plan, except that if Shares or Restricted Stock are repurchased by the Company
at their original purchase price, such Shares shall become available for future
grant under the Plan.

     4. ADMINISTRATION OF THE PLAN.

          (a) ADMINISTRATOR. The Plan shall be administered by the Board or a
Committee appointed by the Board, which Committee shall be constituted to
comply with Applicable Laws.

          (b) POWERS OF THE ADMINISTRATOR. Subject to the provisions of the
Plan and, in the case of a Committee, the specific duties delegated by the
Board to such Committee, and subject to the approval of any relevant
authorities, the Administrator shall have the authority in its discretion:

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               (i)    to determine the Fair Market Value;

               (ii)   to select the Service Providers to whom Options and
Stock Purchase Rights may from time to time be grated hereunder;

               (iii)  to determine the number of Shares to be covered by each
such award granted hereunder;

               (iv)   to approve forms of agreement for use under the Plan;

               (v)    to determine the terms and conditions, of any Option or
Stock Purchase Right granted hereunder. Such terms and conditions include,
but are not limited to, the exercise price, the time or times when Options or
Stock Purchase Rights may be exercised (which may be based on performance
criteria), any vesting acceleration or waiver of forfeiture restrictions, and
any restriction or limitation regarding any Option or Stock Purchase Right or
the Common Stock relating thereto, based in each case on such factors as the
Administrator, in its sole discretion, shall determine;

               (vi)   to determine whether and under what circumstances an
Option may be settled in cash under subsection 9(e) instead of Common Stock;

               (vii)  to reduce the exercise price of any Option to the then
current Fair Market Value if the Fair Market Value of the Common Stock covered
by such Option has declined since the date the Option was granted;

               (viii) to initiate an Option Exchange Program;

               (ix)   to prescribe, amend and rescind rules and regulations
relating to the Plan, including rules and regulations relating to sub-plans
established for the purpose of qualifying for preferred tax treatment under
foreign tax laws;

               (x)    to allow Optionees to satisfy withholding tax obligations
by electing to have the Company withhold from the Shares to be issued upon
exercise of an Option or Stock Purchase Right that number of Shares having a
Fair Market Value equal to the amount required to be withheld. The Fair
Market Value of the Shares to be withheld shall be determined on the date
that the amount of tax to be withheld is to be determined. All elections by
Optionees to have Shares withheld for this purpose shall be made in such form
and under such conditions as the Administrator may deem necessary or
advisable; and

               (xi)   to construe and interpret the terms of the Plan and
awards granted pursuant to the Plan.

          (c) EFFECT OF ADMINISTRATOR'S DECISION. All decisions, determinations
and interpretations of the Administrator shall be final and binding on all
Optionees.

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     5. ELIGIBILITY.

          (a) Nonstatutory Stock Options and Stock Purchase Rights may be
granted to Service Providers. Incentive Stock Options may be granted only to
Employees.

          (b) Each Option shall be designated in the Option Agreement as
either an Incentive Stock Option or a Nonstatutory Stock Option. However,
notwithstanding such designation, to the extent that the aggregate Fair
Market Value of the Shares with respect to which Incentive Stock Options are
exercisable for the first time by the Optionee during any calendar year
(under all plans of the Company and any Parent or Subsidiary) exceeds
$100,000, such Options shall be treated as Nonstatutory Stock Options. For
purposes of this Section 5(b), Incentive Stock Options shall be taken into
account in the order in which they were granted. The Fair Market Value of the
Shares shall be determined as of the time the Options with respect to such
Shares is granted.

          (c) Neither the Plan nor any Option or Stock Purchase Right shall
confer upon any Optionee any right with respect to continuing the Optionee's
relationship as a Service Provider with the Company, nor shall it interfere
in any way with his or her right or the Company's right to terminate such
relationship at any time, with or without cause.

     6. TERM OF PLAN. Subject to Section 19 below, the Plan shall become
effective upon its adoption by the Board. It shall continue in effect for a
term of ten (10) years unless sooner terminated under Section 15 of the Plan.

     7. TERM OF OPTION. The term of each Option shall be stated in the Option
Agreement; provided, however, that the term shall be no more than ten (10) years
from the date of grant thereof. In the case of an Incentive Stock Option granted
to an Optionee who, at the time the Option is granted, owns stock representing
more than ten percent (10%) of the voting power of all classes of stock of the
Company or any Parent or Subsidiary, the term of the Option shall be five (5)
years from the date of grant or such shorter term as may be provided in the
Option Agreement.

     8. OPTION EXERCISE PRICE AND CONSIDERATION.

          (a) The per share exercise price for the Shares to be issued upon
exercise of an Option shall be such price as is determined by the
Administrator, but shall be subject to the following:

               (i)   In the case of an Incentive Stock Option

                    (A) granted to an Employee who, at the time of grant of such
Option, owns stock representing more than ten percent (10%) of the voting power
of all classes of stock of the Company or any Parent or Subsidiary, the exercise
price shall be no less than 110% of the Fair Market Value per Share on the date
of grant.

                    (B) granted to any other Employee, the per Share exercise
price shall be no less than 100% of the Fair Market Value per Share on the date
of grant.

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               (ii)  In the case of a Nonstatutory Stock Option

                    (A) granted to Service Provider who, at the time of grant
of such Option, owns stock representing more than ten percent (10%) of the
voting power of all classes of stock of the Company or any Parent or
Subsidiary, the exercise price shall be no less than 110% of the Fair Market
Value per Share on the date of grant.

                    (B) granted to any other Service Provider, the per Share
exercise price shall be no less than 85% of the Fair Market Value per Share
on the date of grant.

               (iii) Notwithstanding the foregoing, Options may be granted
with a per Share exercise price other than as required above pursuant to a
merger or other corporate transaction.

          (b) The consideration to be paid for the Shares to be issued upon
exercise of an Option, including the method of payment, shall be determined
by the Administrator (and, in the case of an incentive Stock Option, shall be
determined at the time of grant). Such consideration may consist of (1) cash,
(2) check, (3) promissory note, (4) other Shares which (x) in the case of
Shares acquired upon exercise of an Option, have been owned by the Optionee
for more than six months on the date of surrender, and (y) have a Fair Market
Value on the date of surrender equal to the aggregate exercise price of the
Shares as to which such Option shall be exercised, (5) consideration received
by the Company under a cashless exercise program implemented by the Company
in connection with the Plan, or (6) any combination of the foregoing methods
of payment. In making its determination as to the type of consideration to
accept, the Administrator shall consider if acceptance of such consideration
may be reasonably expected to benefit the Company.

     9. EXERCISE OF OPTION.

          (a) PROCEDURE FOR EXERCISE; RIGHTS AS A STOCKHOLDER. Any Option
granted hereunder shall be exercisable according to the terms hereof at such
times and under such conditions as determined by the Administrator and set
forth in the Option Agreement. Unless the Administrator provides otherwise,
vesting of Options granted hereunder to Officers and Directors shall be
tolled during any unpaid leave of absence. An Option may not be exercised for
a fraction of a Share.

         An Option shall be deemed exercised when the Company receives:
(i) written or electronic notice of exercise (in accordance with the Option
Agreement) from the person entitled to exercise the Option, and (ii) full
payment for the Shares with respect to which the Option is exercised. Full
payment may consist of any consideration and method of payment authorized by the
Administrator and permitted by the Option Agreement and the Plan. Shares issued
upon exercise of an Option shall be issued in the name of the Optionee or, if
requested by the Optionee, in the name of the Optionee and his or her spouse.
Until the Shares are issued (as evidenced by the appropriate entry on the books
of the Company or of a duly authorized transfer agent of the Company), no right
to vote or receive dividends or any other rights as a stockholder shall exist
with respect to the Shares, notwithstanding the exercise of the Option. The
Company shall issue (or cause to be issued) such Shares promptly after the
Option is exercised. No

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adjustment will be made for a dividend or other right
for which the record date is prior to the date the Shares are issued, except as
provided in Section 12 of the Plan.

         Exercise of an Option in any manner shall result in a decrease
in the number of Shares thereafter available, both for purposes of the Plan and
for sale under the Option, by the number of Shares as to which the Option is
exercised.

          (b) TERMINATION OF RELATIONSHIP AS A SERVICE PROVIDER. If an Optionee
ceases to be a Service Provider, such Optionee may exercise his or her Option
within such period of time as is specified in the Option Agreement (of at least
thirty (30) days) to the extent that the Option is vested on the date of
termination (but in no event later than the expiration of the term of the Option
as set forth in the Option Agreement). In the absence of a specified time in the
Option Agreement, the Option shall remain exercisable for 90 days following the
Optionee's termination. If, on the date of termination, the Optionee is not
vested as to his or her entire Option, the Shares covered by the unvested
portion of the Option shall revert to the Plan. If, after termination, the
Optionee does not exercise his or her Option within the time specified by the
Administrator, the Option shall terminate and the Shares covered by such Option
shall revert to the Plan.

         In the event an Optionee ceases to be an Employee but remains
a Service Provider, such Employee's Incentive Stock Option shall automatically
convert to a Nonstatutory Stock Option on the date 91 days following such change
of status.

          (c) DISABILITY OF OPTIONEE. If an Optionee ceases to be a Service
Provider as a result of the Optionee's Disability, the Optionee may exercise
his or her Option within such period of time as is specified in the Option
Agreement (of at least 180 days) to the extent the Option is vested on the
date of termination (but in no event later than the expiration of the term of
such Option as set forth in the Option Agreement). In the absence of a
specified time in the Option Agreement, the Option shall remain exercisable
to the extent the Option is vested on the date of termination for 365 days
following the Optionee's termination. If, on the date of termination, the
Optionee is not vested as to his or her entire Option, the Shares covered by
the unvested portion of the Option shall revert to the Plan. If, after
termination, the Optionee does not exercise his or her Option within the time
specified herein, the Option shall terminate, and the Shares covered by such
Option shall revert to the Plan.

          (d) DEATH OF OPTIONEE. If an Optionee dies while a Service Provider,
the Option may be exercised within such period of time as is specified in the
Option Agreement (of at least 180 days) to the extent that the Option is
vested on the date of death (but in no event later than the expiration of the
term of such Option as set forth in the Option Agreement) by the Optionee's
estate or by a person who acquires the right to exercise the Option by
bequest or inheritance. In the absence of a specified time in the Option
Agreement, the Option shall remain exercisable to the extent the Option is
vested on the date of termination for 365 days following the Optionee's
termination. If, at the time of death, the Optionee is not vested as to the
entire Option, the Shares covered by the unvested portion of the Option shall
immediately revert to the Plan. If the Option is not so exercised within the
time specified herein, the Option shall terminate, and the Shares covered by
such Option shall revert to the Plan.

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          (e) BUYOUT PROVISIONS. The Administrator may at any time offer to buy
out for a payment in cash or Shares, an Option previously granted, based on
such terms and conditions as the Administrator shall establish and
communicate to the Optionee at the time that such offer is made.

     10. NON-TRANSFERABILITY OF OPTIONS AND STOCK PURCHASE RIGHTS. The Options
and Stock Purchase Rights may not be sold, pledged, assigned, hypothecated,
transferred, or disposed of in any manner other than by will or by the laws of
descent or distribution and may be exercised, during the lifetime of the
Optionee, only by the Optionee.

     11. STOCK PURCHASE RIGHTS.

          (a) RIGHTS TO PURCHASE. Stock Purchase Rights may be issued either
alone, in addition to, or in tandem with other awards granted under the Plan
and/or cash awards made outside of the Plan. After the Administrator determines
that it will offer Stock Purchase Rights under the Plan, it shall advise the
offeree in writing or electronically of the terms, conditions and restrictions
related to the offer, including the number of Shares that such person shall be
entitled to purchase, the price to be paid, and the time within which such
person must accept such offer. The offer shall be accepted by execution of a
Restricted Stock purchase agreement in the form determined by the Administrator.

          (b) REPURCHASE OPTION. Unless the Administrator determines otherwise,
the Restricted Stock purchase agreement shall grant the Company a repurchase
option exercisable upon the voluntary or involuntary termination of the
purchaser's service with the Company for any reason (including death or
disability). The purchase price for Shares repurchased pursuant to the
Restricted Stock purchase agreement shall be the original price paid by the
purchaser and may be paid by cancellation of any indebtedness of the purchaser
to the Company. The repurchase option shall lapse at such rate as the
Administrator may determine.

          (c) OTHER PROVISIONS. The Restricted Stock purchase agreement shall
contain such other terms, provisions and conditions not inconsistent with the
Plan as may be determined by the Administrator in its sole discretion.

          (d) RIGHTS AS A STOCKHOLDER. Once the Stock Purchase Right is
exercised, the purchaser shall have rights equivalent to those of a stockholder
and shall be a stockholder when his or her purchase is entered upon the records
of the duly authorized transfer agent of the Company. No adjustment shall be
made for a dividend or other right for which the record date is prior to the
date the Stock Purchase Right is exercised, except as provided in Section 12 of
the Plan.

     12. ADJUSTMENTS UPON CHANGES IN CAPITALIZATION, MERGER OR ASSET SALE.

          (a) CHANGES IN CAPITALIZATION. Subject to any required action by the
stockholders of the Company, the number of shares of Common Stock covered by
each outstanding Option or Stock Purchase Right, and the number of shares of
Common Stock which have been authorized for issuance under the Plan but as to
which no Options or Stock Purchase Rights have yet been granted or which have
been returned to the plan upon cancellation or expiration of an Option or

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Stock Purchase Right, as well as the price per share of Common Stock covered by
each such outstanding Option of Stock Purchase Right, shall be proportionately
adjusted for any increase or decrease in the number of issued shares of Common
Stock resulting from a stock split, reverse stock split, stock dividend,
combination or reclassification of the Common Stock, or any other increase or
decrease in the number of issued shares of Common Stock effected without receipt
of consideration by the Company. The conversion of any convertible securities of
the Company shall not be deemed to have been "effected without receipt of
consideration." Such adjustment shall be made by the Board, whose determination
in that respect shall be final, binding and conclusive. Except as expressly
provided herein, no issuance by the Company of shares of stock of any class, or
securities convertible into share of stock of any class, shall affect, and no
adjustment by reason thereof shall be made with respect to, the number or price
of shares of Common Stock subject to an Option or Stock Purchase Right.

          (b) DISSOLUTION OR LIQUIDATION. In the event of the proposed
dissolution or liquidation of the Company, the Administrator shall notify each
Optionee as soon as practicable prior to the effective date of such proposed
transaction. The Administrator in its discretion may provide for an Optionee to
have the right to exercise his or her Option or Stock Purchase Right until
fifteen (15) days prior to such transaction as to all of the Optioned Stock
covered thereby, including Shares as to which the Option or Stock Purchase Right
would not otherwise be exercisable. In addition, the Administrator may provide
that any Company repurchase option applicable to any Shares purchased upon
exercise of an Option or Stock Purchase Right shall lapse as to all such Shares,
provided the proposed dissolution or liquidation takes place at the time and in
the manner contemplated. To the extent it has not been previously exercised, an
Option or Stock Purchase Right will terminate immediately prior to the
consummation of such proposed action.

          (c) MERGER OR ASSET SALE. In the event of a merger of the Company with
or into another corporation which does not constitute a "Change of Control" (as
defined in Section 13), or the sale of substantially all of the assets of the
Company, each outstanding Option and Stock Purchase Right shall be assumed or an
equivalent option or right substituted by the successor corporation or a Parent
or Subsidiary of the successor corporation. In the event that the successor
corporation refuses to assume or substitute for the Option or Stock Purchase
Right, the Optionee shall fully vest in and have the right to exercise the
Option or Stock Purchase Right as to all of the Optioned Stock, including Shares
as to which it would not otherwise be vested or exercisable. If an Option or
Stock Purchase Right becomes fully vested and exercisable in lieu of assumption
or substitution in the event of a merger or sale of assets, the Administrator
shall notify the Optionee in writing or electronically that the Option or Stock
Purchase Right shall be fully exercisable for a period of fifteen (15) days from
the date of such notice, and the Option or Stock Purchase Right shall terminate
upon the expiration of such period. For the purposes of this paragraph, the
Option or Stock Purchase Right shall be considered assumed if, following the
merger or sale of assets, the option or right confers the right to purchase or
receive, for each Share of Optioned Stock subject to the Option or Stock
Purchase Right immediately prior to the merger or sale of assets, the
consideration (whether stock, cash, or other securities or property) received in
the merger or sale of assets by holders of Common Stock for each Share held on
the effective date of the transaction (and if holders were offered a choice of
consideration, the type of consideration chosen by the holders of a majority of
the outstanding Shares); provided,

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however, that if such consideration received in the merger or sale of assets is
not solely common stock of the successor corporation or its Parent, the
Administrator may, with the consent of the successor corporation, provide for
the consideration to be received upon the exercise of the Option or Stock
Purchase Right, for each Share of Optioned Stock subject to the Option or Stock
Purchase Right, to be solely common stock of the successor corporation or its
Parent equal in fair market value to the per share consideration received by
holders of Common Stock in the merger or sale of assets.

     13. VESTING ACCELERATION ON CHANGE OF CONTROL.

          (a) VESTING ACCELERATION. In the event of a "Change of Control,"
(i) all of the Optionee's rights to purchase stock under all stock option
agreements with the Company pursuant to the Plan shall be automatically vested
in their entirety on an accelerated basis and be fully exercisable, and (ii) all
of the Company's rights to repurchase unvested stock under all restricted stock
purchase agreements pursuant to the Plan with the Optionee shall lapse in their
entirety on an accelerated basis:

               (i)   as of the date immediately preceding such "Change of
Control" in the event any such stock option agreement or restricted stock
purchase agreement is or will be terminated or cancel (except by mutual consent)
or any successor to the Company fails to assume and agree to perform the
Company's obligations under all such stock option agreements and restricted
stock purchase agreements; or

               (ii)  as of the date immediately preceding such "Change of
Control" in the event the Optionee does not or will not receive upon exercise of
the Optionee's stock purchase rights under any such stock option agreement or in
exchange for the Optionee's restricted stock acquired pursuant to any such
restricted stock purchase agreement the same identical securities and/or other
consideration as is received by all other stockholders in any merger,
consolidation, sale, exchange or similar transaction occurring upon or after
such "Change of Control"; or

               (iii) as of the date immediately preceding any "Involuntary
Termination" of the Optionee occurring upon or after any such
"Change of Control"; or

               (iv)  as of the first anniversary of the date of the first such
"Change of Control," provided that the Optionee shall not have voluntarily
terminated Optionee's employment with the Company prior to the end of such year;

whichever shall first occur (all quoted terms as defined below).

          (b) CHANGE OF CONTROL. "Change of Control" means the occurrence of
any of the following events:

               (i)   Any "person" (as such term is used in Sections 13(d) and
14(d) of the Securities Exchange Act of 1934, as amended), other than Austin
Ventures VI, L.P. or an affiliated fund, is or becomes the "beneficial owner"
(as defined in Rule 13d-3 under said Act),

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directly or indirectly, of securities of the Company representing 50% or more of
the total voting power represented by the Company's then outstanding voting
securities; or

               (ii)  A change in the composition of the Board of Directors of
the Company as a result of which fewer than a majority of the directors are
"Incumbent Directors." "Incumbent Directors" shall mean directors who either (A)
are directors of the Company as of the date hereof, or (B) are elected, or
nominated for election, to the Board of Directors with the affirmative votes
(either by a specific vote or by approval of the proxy statement of the Company
in which such person is named as a nominee for election as a director without
objection to such nomination) of at least three-quarters of the Incumbent
Directors at the time of such election or nomination (but shall not include an
individual whose election or nomination is in connection with an actual or
threatened proxy contest relating to the election of directors of the Company);
or

               (iii) The stockholders of the Company approve a merger or
consolidation of the Company with any other entity, other than a merger or
consolidation which would result in the voting securities of the Company
outstanding immediately prior thereto continuing to represent (either by
remaining outstanding or by being converted into voting securities of the
surviving entity of such surviving entity's parent) at least fifty percent (50%)
of the total voting power represented by the voting securities of the Company or
such surviving entity or such surviving entity's parent outstanding immediately
after such merger or consolidation, or the stockholders of the Company approve a
plan of complete liquidation of the Company or an agreement for the sale or
disposition by the Company of all or substantially all of the Company's assets.

          (c) INVOLUNTARY TERMINATION. "Involuntary Termination" shall mean
(i) a termination by the Company of the Optionee's employment with the Company
other than for Cause; (ii) a material reduction of or variation in the
Optionee's duties, authority or responsibilities, relative to the Optionee's
duties, authority or responsibilities as in effect immediately prior to such
reduction or variation; (iii) a reduction by the Company in the base salary of
the Optionee as in effect immediately prior to such reduction; (iv) a material
reduction by the Company in the kind or level of employee benefits, including
bonuses, to which the Optionee was entitled immediately prior to such reduction,
with the result that the Optionee's overall benefits package is materially
reduced; or (v) the relocation of the Optionee to a facility or location more
than thirty (30) miles from the Optionee's then present location.

          (d) CAUSE. "Cause" shall mean (i) any willful act of personal
dishonesty, fraud or misrepresentation taken by the Optionee in connection with
his or her responsibilities as an employee which was intended to result in
substantial gain or personal enrichment of the Optionee at the expense of the
Company and was materially demonstrably injurious to the Company; (ii) the
Optionee's conviction of a felony on account of any act which was materially and
demonstrably injurious to the Company; or (iii) the Optionee's willful and
continued failure to substantially perform his or her principal duties and
obligations of employment (other than any such failure resulting from incapacity
due to physical or mental illness), which failure is not remedied in a
reasonable period of time after receipt of written notice from the Company. For
the purposes of this Section 13(d), no act or failure to act shall be considered
"willful" unless

                                       11

<Page>

done or omitted to be done in bad faith and without reasonable belief that the
act or omission was in or not opposed to the best interests of the Company.

          (e) VOLUNTARY RESIGNATION; TERMINATION FOR CAUSE. If the Optionee's
continuous status as an employee of the Company terminates by reason of the
Optionee's voluntary resignation (and not Involuntary Termination) or if the
Optionee's continuous status as an employee of the Company in terminated for
Cause, in either case prior to such time as accelerated vesting occurs as
provided in Section 13(a) hereof, then the Optionee shall not be entitled to
received accelerated vesting under Section 13(a) hereof.

     14. TIMING OF GRANTING OPTIONS AND STOCK PURCHASE RIGHTS. The date of
grant of an Option or Stock Purchase Right shall, for all purposes, be the date
on which the Administrator makes the determination granting such Option or Stock
Purchase Right, or such other date as is determined by the Administrator. Notice
of the determination shall be given to each Service Provider to whom an Option
or Stock Purchase Right is so granted within a reasonable time after the date of
such grant.

     15. AMENDMENT AND TERMINATION OF THE PLAN.

          (a) AMENDMENT AND TERMINATION. The Board may at any time amend,
alter, suspend or terminate the Plan.

          (b) STOCKHOLDER APPROVAL. The Board shall obtain stockholder approval
of any Plan amendment to the extent necessary and desirable to comply with
Applicable Laws.

          (c) EFFECT OF AMENDMENT OR TERMINATION. No amendment, alteration,
suspension, or termination of the Plan shall impair the rights of any Optionee,
unless mutually agreed otherwise between the Optionee and the Administrator,
which agreement must be in writing and signed by the Optionee and the Company.
Termination of the Plan shall not affect the Administrator's ability to exercise
the powers granted to it hereunder with respect to Options granted under the
Plan prior to the date of such termination.

     16. CONDITIONS UPON ISSUANCE OF SHARES.

          (a) LEGAL COMPLIANCE. Shares shall not be issued pursuant to the
exercise of an Option unless the exercise of such Option and the issuance and
delivery of such Shares shall comply with Applicable Laws and shall be further
subject to the approval of counsel for the Company with respect to such
compliance.

          (b) INVESTMENT REPRESENTATIONS. As a condition to the exercise of an
Option, the Administrator may require the person exercising such Option to
represent and warrant at the time of any such exercise that the Shares are being
purchased only for investment and without any present intention to sell or
distribute such Shares if, in the opinion of counsel for the Company, such a
representation is required.

     17. INABILITY TO OBTAIN AUTHORITY. The inability of the Company to obtain
authority from any regulatory body having jurisdiction, which authority is
deemed by the Company's counsel to be necessary to the lawful issuance and sale
of any Shares hereunder, shall relieve the Company



<Page>

     18. RESERVATION OF SHARES. The Company, during the term of this Plan,
shall at all  times  reserve  and keep  available  such  number  of Shares as
shall be sufficient to satisfy the requirements of the Plan.

     19.  STOCKHOLDER  APPROVAL.  The Plan shall be subject to  approval  by
the stockholders of the Company within twelve (12) months after the date the
Plan is adopted.  Such  stockholder  approval shall be obtained in the degree
and manner required under Applicable Laws.

     20.  INFORMATION TO OPTIONEES AND PURCHASERS.  The Company shall provide
to each Optionee and to each  individual who acquires  Shares pursuant to the
Plan, not less  frequently  than annually during the period such Optionee or
purchaser has one or more Options or Stock Purchase Rights  outstanding,
and, in the case of an individual who acquires Shares, copies of annual
financial statements. The Company shall not be required to provide such
statements to key employees whose duties  in  connection  with the  Company
assure  their  access  to  equivalent information.

<PAGE>


                              TANTAU SOFTWARE, INC.

                    RETROACTIVE AMENDMENT TO 1999 STOCK PLAN

           The Tantau  Software,  Inc.  1999  Stock Plan (the  "PLAN") is
hereby  amended,  with  such  amendment  to apply to all  currently
outstanding options and options granted from November 20, 2000 under the
Plan, as follows:

                1. Section 3 (STOCK  SUBJECT TO THE PLAN) is hereby amended by
amending and restating the first sentence of  such Section to read as follows:

         "Subject  to the  provisions  of  Section 12 of the Plan,  the  maximum
         aggregate number of Shares that may be subject to option and sold under
         the Plan is 10,925,000 Shares."

                2.  Subsection  (b) of  Section 8 (OPTION  EXERCISE  PRICE AND
CONSIDERATION)  is hereby amended by amending and restating the second  sentence
of such subsection in its entirety to read as follows:

         "Such  consideration  may consist of (1) cash; (2)  certified,  bank or
         cashiers check; (3) money order (4) subject to the prior consent of the
         Board or the  Committee,  surrender of Shares or delivery of a properly
         executed   form  of   attestation   of   ownership  of  Shares  as  the
         Administrator  may require  (including  withholding of Shares otherwise
         deliverable upon exercise),  such Shares to have a Fair Market Value on
         the date of surrender or  attestation  equal to the aggregate  exercise
         price of the Shares as to which such  Option  shall be  exercised  (but
         only  to  the  extent  that  such  exercise   would  not  result  in  a
         compensation  charge for financial  reporting  purposes with respect to
         the Shares used to pay the exercise price, unless otherwise  determined
         by the Administrator); (5) subject to the prior consent of the Board or
         the  Committee,  payment  through a  broker-dealer  sale and remittance
         procedure  (including,  if approved by the Administrator and subject to
         regulatory  approval,  a loan  facility to be provided by the  Company)
         pursuant to which an Optionee:  (x) shall provide written  instructions
         to a Company-designated  brokerage firm to effect the immediate sale of
         some or all of the  Shares  and remit to the  Company,  out of the sale
         proceeds  available on the settlement  date,  sufficient funds to cover
         the  aggregate  exercise  price  payable for the Shares;  and (y) shall
         provide written  directions to the Company to deliver the  certificates
         for the Shares directly to such brokerage firm in order to complete the
         sale  transaction;  or (6) any combination of the foregoing  methods of
         payment. In making its determination as to the type of consideration to
         accept,  the  Administrator   shall  consider  if  acceptance  of  such
         consideration may be reasonably be expected to benefit the Company."

                  3.  Upon the  consummation  of a merger  of the  Company  with
Saturn Merger Sub,  Inc. (a  wholly-owned  subsidiary  of 724 Solutions  Inc., a
corporation  amalgamated under the Business  Corporations Act of the Province of
Ontario, Canada ("724 SOLUTIONS")),  all references in the Plan to the "Company"
shall mean 724 Solutions.


<PAGE>

                  4.       Subsection (a) of Section 9 (EXERCISE OF OPTION) is
 hereby amended and restated to read as follows:


         "(a)     PROCEDURE FOR EXERCISE; RIGHTS AS A STOCKHOLDER.

                  (i)  Any  Option  granted   hereunder   shall  be  exercisable
         according to the terms  hereof at such times and under such  conditions
         as  determined  by the  Administrator  and  set  forth  in  the  Option
         Agreement.  Unless the  Administrator  provides  otherwise,  vesting of
         Options  granted  hereunder to Officers and  Directors  shall be tolled
         during any unpaid leave of absence.  An Option may not be exercised for
         a fraction of a Share.

                  (ii) An Option  shall be  deemed  exercised  when the  Company
         receives:  (A) written or electronic  notice of exercise (in accordance
         with the Option  Agreement and in a form approved by the  Administrator
         from time to time in its sole  discretion)  from the person entitled to
         exercise  the Option,  and (B) full payment for the Shares with respect
         to which the  Option is  exercised.  Full  payment  may  consist of any
         consideration and method of payment authorized by the Administrator and
         permitted by the Option Agreement and the Plan.

                  (iii) Shares issued upon exercise of an Option shall be issued
         in the name of the  Optionee  or,  if  requested  by the  Optionee  and
         approved by the Administrator in its sole discretion in accordance with
         Applicable Laws, in the name of the Optionee and his or her spouse.

                  (iv)  Until  the  shares  are  issued  (as  evidenced  by  the
         appropriate  entry on the books of the Company or of a duly  authorized
         transfer agent of the Company),  no right to vote or receive  dividends
         or any other  rights as a  stockholder  shall exist with respect to the
         Shares,  notwithstanding  the exercise of the Option. The Company shall
         issue (or cause to be issued) such Shares  promptly after the Option is
         exercised.

                  (v) No  adjustment  will be made for a dividend or other right
         for which the record  date is prior to the date the Shares are  issued,
         except as provided in Section 12 of the Plan.

                  (vi) Any right of first refusal (but not the repurchase option
         applicable to unvested Shares) in favor of the Company upon exercise of
         an Option or with  respect  to any Shares  issued  under the Plan shall
         lapse if the  Company or any  successor  in  interest to the Company is
         listed on a national securities exchange or national market system.

                  (vii)  Exercise of an Option in any manner  shall  result in a
         decrease  in the  number  of  Shares  thereafter  available,  both  for
         purposes  of the Plan and for sale under the  Option,  by the number of
         Shares as to which the Option is exercised."


                                       2

<PAGE>


                  5. Section 11 (STOCK PURCHASE RIGHTS) is hereby deleted in its
entirety.

                  6. Except as modified  by this Plan  Amendment,  all the terms
and provisions of the Plan shall continue in full force and effect.




                                        3

<PAGE>


                              TANTAU SOFTWARE, INC.

                    PROSPECTIVE AMENDMENT TO 1999 STOCK PLAN

                  The Tantau  Software,  Inc.  1999  Stock Plan (the  "PLAN")
 is hereby  amended  with  respect to options granted from November 20, 2000
under the Plan as follows:

                  1. Subsection (c) of Section 12  (ADJUSTMENTS  UPON CHANGES IN
CAPITALIZATION,  MERGER OR ASSET  SALE) is hereby  amended  and  restated in its
entirety to read as follows:

         "(c)     MERGER OR ASSET SALE.

         (i)  Appropriate  adjustments  in the number of Shares and the exercise
         price  subject  to  each  outstanding  option  shall  be  made  by  the
         Administrator  to give  effect to the  number of Shares of the  Company
         resulting from subdivisions, consolidations or reclassifications of the
         Shares,  the  payment of stock  dividends  by the  Company  (other than
         dividends in the ordinary course) or other changes in the capital stock
         of the Company which the Administrator may, in its discretion, consider
         relevant for purposes of ensuring  that the rights of Optionees are not
         prejudiced thereby (including amalgamations,  mergers, reorganizations,
         liquidations  and  similar  material  transactions),   subject  to  the
         approval,  if required of any stock exchange on which the securities of
         the Company may be listed.

         (ii) If (A) the Company proposes to enter into a transaction that would
         constitute a "Change of Control" (as defined in subsection  (d) of this
         Section 12), (B) the Company  proposes to make an issuer bid for all or
         substantially all holders of shares or proposes to enter into a merger,
         amalgamation or other  corporate  arrangement or  reorganization  or to
         liquidate,  dissolve  or  wind-up;  (C) an  offer  to  purchase  all or
         substantially all of the outstanding shares of the Company is made by a
         third  party;  or (D) there occurs or is proposed a sale or transfer of
         all, or substantially  all, of the  undertaking,  property or assets of
         the Company,  the Board may, with appropriate  notice and in a fair and
         equitable manner, determine the manner in which all outstanding Options
         shall be treated  including,  the acceleration of the expiration of the
         Option  and  of the  exercisability  or  vesting  of  the  Option.  All
         determinations  of the Board under this  paragraph  (ii)  (including  a
         determination that it would be appropriate not to make an adjustment in
         the circumstances) shall be conclusive and final.

         (iii)  Immediately  following the  consummation of a Change of Control,
         all Options shall terminate and cease to be outstanding,  except to the
         extent  assumed by the  successor  corporation  (or parent  thereof) or
         otherwise continued in effect."

                  2.       A new  subsection  (d) is hereby added to Section 12
 of the Plan to read in its entirety as follows:

         "(d)     CHANGE OF CONTROL.  For  purposes of this  Section  12,
         "Change of Control"  shall mean the occurrence of any of the following
         events:


<PAGE>

         (i) Any "person"  (as such term is used in Sections  13(d) and 14(d) of
         the  Securities  Exchange Act of 1934,  as amended),  other than Austin
         Ventures VI, L.P. or an affiliated  fund, is or becomes the "beneficial
         owner"  (as  defined  in  Rule  13d-3  under  said  Act),  directly  or
         indirectly,  of securities of the Company  representing  50% of more of
         the total voting power  represented by the Company's  then  outstanding
         voting securities; or

         (ii) A change  in the  composition  of the  Board of  Directors  of the
         Company as a result of which fewer than a majority of the directors are
         "Incumbent  Directors."  "Incumbent Directors" shall mean directors who
         either (A) are  directors of the Company as of the date hereof,  or (B)
         are elected, or nominated for election,  to the Board of Directors with
         the affirmative  votes (either by a specific vote or by approval of the
         proxy statement of the Company in which such person is named as nominee
         for election as a director without  objection to such nomination) of at
         least  three-quarters  of the  Incumbent  Directors at the time of such
         election  or  nomination  (but shall not  include an  individual  whose
         election or nomination  is in  connection  with an actual or threatened
         proxy contest relating to the election of directors of the Company); or

         (iii) The stockholders of the Company approve a merger or consolidation
         of  the  Company  with  any  other  entity,  other  than  a  merger  or
         consolidation  which  would  result  in the  voting  securities  of the
         Company  outstanding  immediately prior thereto continuing to represent
         (either by  remaining  outstanding  or by being  converted  into voting
         securities of the surviving  entity or such surviving  entity's parent)
         at least fifty percent (50%) of the total voting power  represented  by
         the voting  securities of the Company or such surviving  entity or such
         surviving entity's parent outstanding  immediately after such merger or
         consolidation,  or the  stockholders  of the Company  approve a plan of
         complete  liquidation  of the Company or an  agreement  for the sale or
         disposition  by the Company of all or  substantially  all the Company's
         assets."

                  3. Section 13 (VESTING  ACCELERATION  ON CHANGE OF CONTROL) is
hereby amended and restated in its entirety to read as follows:

          "13. CHANGE OF CONTROL UPON MERGER WITH 724 SOLUTIONS. Notwithstanding
          anything in this Plan to the contrary,  upon the  consummation  of the
          merger  of  the  Company  with  724  Solutions  Inc.  (or  any  of its
          wholly-owned  subsidiaries),  Section  12 of the  Plan  shall  have no
          further  force  and  effect,  and all  outstanding  Options  shall  be
          governed by the following provisions:

         (a) If an offer is made to purchase  outstanding  voting  shares of the
         Company and it is accepted  and  completed  in respect of a  sufficient
         number of holders of such shares to  constitute  the offeror  (together
         with such other persons as may be  considered to be "acting  jointly or
         in concert"  with the offeror  within the meaning given to such term in
         Section  91 of the  SECURITIES  ACT  (Ontario))  a  stockholder  of the
         Company  entitled  to  exercise  more  than  50% of the  voting  rights
         attached to the outstanding  voting shares  (provided that prior to the
         offer, the offeror and such


                                         2

<PAGE>


          other persons (collectively, the "Control Group") were not entitled to
          exercise  more  than  50%  of  the  voting  rights   attached  to  the
          outstanding  voting shares) or if there is a consolidation,  merger or
          amalgamation of the Company with or into any other corporation whereby
          the  voting  stockholders  of the  Company  immediately  prior  to the
          consolidation,  merger or  amalgamation  receive  shares  entitled  to
          exercise  less than 50% of the voting  rights  attaching to the voting
          shares  of  the  consolidated,   merged  or  amalgamated  corporation,
          including a sale  whereby all or  substantially  all of the  Company's
          undertakings and assets become the property of any other  corporation,
          then Optionee  shall,  immediately be entitled to exercise such Option
          with  respect to all of the  Shares  subject to the Option and not yet
          purchased thereunder.

                  (b) In  addition,  if an offer is made to purchase 50% or more
         of the  outstanding  voting shares of the Company (the "Offer") and the
         terms of such  Offer  permit  the  tendering  of  Shares  by  notice of
         guaranteed  delivery  or  similar  procedure  in  order to  permit  the
         participation  in such Offer by the holders of Options,  Optionee shall
         have  the  right  to  exercise  his or her  Options  (for  purposes  of
         tendering  to the  Offer) as to the full  amount of Shares  purchasable
         thereunder whether or not then vested, conditional only upon completion
         of the  Offer,  and to  tender  the  Shares  to be  purchased  from the
         Optionee and which are  issuable  pursuant to such Options to the Offer
         by notice of guaranteed  delivery or similar  procedure,  provided that
         arrangements  for payment of the  exercise  price  satisfactory  to the
         Company and in compliance  with  applicable  law and any stock exchange
         requirements  are made, and the Company will take all reasonable  steps
         necessary to facilitate such  conditional  exercise of Options and such
         tender of Shares."

                  4.  Subsection (c) of Section 15 (AMENDMENT AND TERMINATION OF
THE PLAN) is hereby amended and restated in its entirety to read as follows:

         "(c) EFFECT OF AMENDMENT OR  TERMINATION.  The Plan, as amended,  shall
         govern the rights and  obligations  of the Company and  Optionees  with
         respect to Options  outstanding  at such time of amendment  and without
         further consent of any such Optionee  unless such amendment  materially
         and  adversely  affects  the rights of such  Optionee  under any Option
         outstanding at such time."

                  5.  For  all  purposes  of the  Plan,  the  Merger  shall  not
constitute a Change in Control.

                  6. Except as modified  by this Plan  Amendment,  all the terms
and provisions of the Plan shall continue in full force and effect.



                                         3