Project(Extend(Union(Graph(<http://example.org>,
                           BGP( ?x <http://www.w3.org/2000/01/rdf-schema#label> ?label)),
                     Graph(<http://example.org>,
                           BGP( ?s <http://example.org/predicate> ?o))),
               ?y,
               ?label),
        {?x, ?y})