Distinct(Project(Filter(! bound(?llab) ,
                        LeftJoin(BGP( ?lab <http://www.w3.org/2000/01/rdf-schema#subPropertyOf>+ <http://www.w3.org/2000/01/rdf-schema#label> .
                                      ?s ?lab ?label),
                                 BGP( ?s <http://www.w3.org/2000/01/rdf-schema#label> ?llab))),
                 {?s, ?lab, ?label}))