Re: SHACL target extension

In addition to what Havard wrote: for the Ontotext platform we need
something a bit more complex, which we call "semantic object types", and
which are mapped to GraphQL types and to SHACL shapes. These are inherited
along a hierarchy and check a conjunction (several type predicates,
inherited) of disjunctions (alternative type values).

Use cases ("<type> is defined as" can be read as "<shape> targets the
following"):
- Person is defined as rdf:type schema:Person or dbo:Person
- Industry is defined as rdf:type skos:Concept; and skos:inScheme
<industry/DBP> or <industry/WD>
- Country is defined as rdf:type gn:Feature and gn:featureCode one
of 'gn:A.PCLI', 'gn:A.PCLD', 'gn:A.PCLIX', 'gn:A.PCLS', 'gn:A.PCL',
'gn:A.TERR', 'gn:A.PCLF'

This could be expressed eg like this:

so:semanticTarget
  [rdf:type gn:Feature],
  [gn:featureCode gn:A.PCLI, gn:A.PCLD, gn:A.PCLIX, gn:A.PCLS, gn:A.PCL,
gn:A.TERR, gn:A.PCLF]