[wsrp-wsia] EntityInstanceKey ... MAY/MUST

We introduced this field at the November F2F in a manner that I (and others
questioning things by email) find unusual and confusing. This was
introduced as a required field that should be unique ... this is in the
spec as:

"entityInstanceKey: An opaque string the Consumer MUST supply as a
reference to this use of the entity. This reference SHOULD be unique within
the current set of interactions on behalf of a user as it MAY be used by
the entity to properly separate data for multiple instances of the entity
within any Producer-defined data sharing mechanisms."

I would find this much cleaner (and more useful) if it were an optional
field that must be unique whenever it is supplied, namely:

"entityInstanceKey: A unique, opaque string the Consumer MAY supply as a
reference to this use of the entity. This reference MAY be used by the
entity to properly separate data for multiple instances of the entity
within any Producer-defined data sharing mechanisms."

In other words; If the Consumer supplies it, it must be unique so it may be
used as a key into a shared data area. If the Consumer does not supply, the
Producer is on its own for generating such a key.

This compares to the current where something is supplied, but the Producer
has no idea whether or not it may be used in such a manner.

Any objections to this change?

Rich Thompson