+P, ?O, -RealP)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
symmetric. See rdf_set_predicate/2.
+Predicate, ?Object)Succeeds if the triple
rdf(Subject, Predicate, Object) is
true exploiting the rdfs:subPropertyOf predicate as well as inverse
predicates declared using rdf_set_predicate/2