<PAGE>
Exhibit 5.1
October 3, 2000
Documentum, Inc.
6801 Koll Center Parkway
Pleasanton, California 94566
Ladies and Gentlemen:
You have requested our opinion with respect to certain matters in
connection with the filing by Documentum, 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 1,300,000 shares of the
Company's Common Stock, $.001 par value, (the "Shares") pursuant to its Employee
Stock Purchase Plan, 1995 Non-employee Directors' Stock Option Plan and 1996
Non-Officer Equity Incentive Plan (the "Plans").
In connection with this opinion, we have examined the Registration
Statement and related Prospectus, 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, the
Registration Statement and related Prospectuses, will be validly issued, fully
paid, and nonassessable (except as to shares issued pursuant to certain 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/ MARK P. TANOURY
---------------------------------------
Mark P. Tanoury
