We should agree on Qualifier policies to guide implementation of TRAPI 1.3

[edeutsch]

As we all implement TRAPI 1.3, I think it would be very helpful to document our common answers to these questions:

1. If a client does not specify qualifiers in a query, but a server has edges that match the requested predicate but with qualifiers on them, SHOULD/MUST it furnish those qualifiers to the client?

2. If a client does specify qualifiers in a query, but a server has only edges that match the unqualified predicate (or doesn't implement qualifiers at all yet), SHOULD/MUST the server return the matching unqualified edges or nothing?

I think we should discuss and document these policies. I think this is a job for Architecture, but maybe it more apropos for another group?

[edeutsch]

I had forgotten that we had already voted on question 2 over in the TRAPI repo here: NCATSTranslator/ReasonerAPI#328

The results (with a 4-1-0 vote) seems to be:

If a KP receives non-empty QEdge.qualifier_constraints, it MAY return edges that satisfy the unqualified edge.