Distinct(Project(Filter((?l1 != ?l2),
                        Join(Graph(?g2,
                                   BGP( ?p1 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/1999/02/22-rdf-syntax-ns#Property> .
                                        ?p1 <http://www.w3.org/2000/01/rdf-schema#label> ?l2)),
                             Graph(?g1,
                                   BGP( ?p1 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/1999/02/22-rdf-syntax-ns#Property> .
                                        ?p1 <http://www.w3.org/2000/01/rdf-schema#label> ?l1)))),
                 {?g1, ?g2, ?l1, ?l2, ?p1}))