- rdf_has(?S, +P, ?O) is nondet
- rdf_has(?S, +P, ?O, -RealP) is nondet
- Similar to rdf/3 and rdf/4, but P matches all predicates that
are defined as an rdfs:subPropertyOf of P. This predicate also
recognises the predicate properties
inverse_of and
symmetric. See rdf_set_predicate/2.