Exhibit 5.1

                                Form of Opinion

                          [COOLEY GODWARD LETTERHEAD]

May 19, 2000

Aspect Development, Inc.
1395 Charleston Road
Mountain View, CA  94043

Ladies and Gentleman:

You have requested our opinion with respect to certain matters in connection
with the filing by Aspect Development, Inc. (the "Company") of a Registration
Statement on Form S-8 (the "Registration Statement") with the Securities and
Exchange Commission covering the offering of up to 4,054,244 shares of the
Company's Common Stock, $.001 par value, pursuant to the Company's 1997
Nonstatutory Stock Option Plan, the Transition Analysis Component Technology,
Inc. 1997 Stock Option Plan and the Bruce Blackford and Jeff Hanser Option
Agreements for TACTech Common Stock (collectively the "Plans").

In connection with this opinion, we have examined the Plans and the Registration
Statement, your Certificate of Incorporation and By-laws, as amended, and such
other documents, records, certificates, memoranda and other instruments as we
deem necessary as a basis for this opinion.  We have assumed the genuineness and
authenticity of all documents submitted to us as originals, the conformity to
originals of all documents submitted to us as copies thereof, and the due
execution and delivery of all documents where due execution and delivery are a
prerequisite to the effectiveness thereof.

On the basis of the foregoing, and in reliance thereon, we are of the opinion
that the Shares, when sold and issued in accordance with the Plans and the
Registration Statement, will be validly issued, fully paid, and nonassessable
(except as to shares issued pursuant to deferred payment arrangements, which
will be fully paid and nonassessable when such deferred payments are made in
full).

We consent to the filing of this opinion as an exhibit to the Registration
Statement.

Very truly yours,

Cooley Godward LLP

By:
       /s/ James C. Kitch
     _________________________
     James C. Kitch, Esq.