% Match nested RDF 1.2 triple terms and derive the innermost relationship.
rdf(S, iri("https://example.org/knows"), O, G) :-
  rdf(
    _,
    iri("https://example.org/reviews"),
    triple(
      _,
      iri("https://example.org/claims"),
      triple(S, iri("https://example.org/knows"), O)
    ),
    G
  ).