PROV-ISSUE-41 (distinct-roles): Distinct roles should be SHOULD and not MUST [Conceptual Model]

PROV-ISSUE-41 (distinct-roles): Distinct roles should be SHOULD and not MUST [Conceptual Model]

http://www.w3.org/2011/prov/track/issues/41

Raised by: Paul Groth
On product: Conceptual Model

Currently, use has the following definition with respect to roles:

"A reference to a given BOB may appear in multiple use assertions that refer to a given process execution, but each of those use assertions must have a distinct role."

A process execution could conceivably read the same file twice. Thus, the file would play the same role twice with respect to a process execution. It's not clear why this constraint is an absolute or the impact of making it a non-hard requirement.

 Although, I can see why it would be recommended practice in order to ensure disambiguation of roles. 

Suggested resolution, change the sentence to as follows:

"A reference to a given BOB may appear in multiple use assertions that refer to a given process execution, but each of those use assertions should have a distinct role."