Key of K/V Pair as Predicate?

[joshmoore]

From @CFGrote's presentation (https://zenodo.org/records/10808486), it might be useful to have the keys as predicates:

[CFGrote]

To provide some context, the key-value pair MPB,15447 appears in another graph, too. Hence being able to get the
value (15447) from a query like

?ann a ome_core:map ;
           ns1:mpb ?mpb_val .
...

would then allow join-like queries against that other graph.

In the current implementation, I first have to filter all keys returned from the query by, e.g.

filter(contains(?key, "MPB"))

That's not such a big deal but becomes more of a problem if the omero-rdf graph is second in a join scenario like above.

I'll be happy to share more context if needed (or contribute code).