Functional Spec derives from Software requirements.

Software requirement derives from Marketing requirements.

MRs will be prepared by Business Analysts with help of

EndUsers.

So, Functional Spec is a small piece of requirement to fill

business requirement. Finally the Functionality will be

validated/Verified against MRs tested by End User during

user acceptency testing.

Finally, S/W Functional specs will be prepared by Process

Owners / Business Analysts.