Re: on entailments and triple terms

> For example, many queries do not take into account rdfs:subpropertyOf when
> querying non-ontology facts.  This has probably led to underuse of
> rdfs:subpropertyOf.  Even worse, SPARQL is incapable of uniformly querying
> ontologies that have subproperties of rdfs:subclassOf.  So, for example,
> SPARQL cannot uniformly query for class instances in Wikidata, as Wikidata has
> properties that are subproperties of its version of rdfs:subclassOf.

One practical challenge of using rdfs:subPropertyOf in real-world queries is that
in many cases the subject and object of the triple pattern will be variables or
blank nodes. It is then necessary to make the predicate a variable to match the
sub-property pattern, which quickly gets complex if we are interested in multiple
predicates.

A query like this will likely not perform on a non-trivial dataset:

prefix ex: <http://example.com/>
select ?o1 ?o2 ?o3
where {
  [] ?p1 ?o1 ;
    ?p2 ?o2 ;
    ?p3 ?o3 .

  ?p1 rdfs:subPropertyOf* ex:prop1 .
  ?p2 rdfs:subPropertyOf* ex:prop2 .
  ?p3 rdfs:subPropertyOf* ex:prop3 .
}

Adding RDF-star or RDFS+++ entailments into the mix as part of a query can
only increase the complexity.

Regards,

John Walker
Principal Consultant & co-founder

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