[oslc-cm] State Predicates

[Samuel Padgett]

Thanks for your input, Paul. After reading Samit and your replies, I agree
we need further clarification.

> I am not sure how to interpret the statement : "If present,
> predicates MUST be queryable".   As you pointed out, each predicate
> is defined as zero-or-one on an individual basis.  Would saying that
> a predicate is "present" mean that the provider knows a value for
> it, or would it mean that the predicate would be present in every
> Change Request included in the response if the client was to ask for
> it?  In either case, how could the CM consumer detect this condition
> before deciding how to build a query URL?  And what would be the
> result of including a predicate in a query when the "If present..."
> condition will not been met?  Would the server return an error code,
> or would the query results be inaccurate, etc?

I think the right approach is for providers to simply leave predicate
values out of the response if they aren't supported for the change request
(as opposed to responding with an error). We could add language here saying
that.

Does that satisfy your use case?

> ...                              If the CM spec needs to explicitly
> accommodate providers that don't support state predicates at all
> then it might be better to require that they advertise this
> limitation in their resource shapes document or services catalog.
> Alternatively, if the CM workgroup believes that general support for
> state predicates is actually required by the V2 scenarios then the
> spec could be clarified to call that out instead.

My concern is that this proposal introduces new MUST requirements into an
already-final spec (rather than simply clarifying what's already there). We
might be able to look at it for 3.0, though.

- Thanks, Sam