empty https://w3id.org/framester/pb/pbdata/empty.01 <https://w3id.org/framester/pb/pbschema/RoleSet> rdfs:label xsd:string empty rdf:type <https://w3id.org/framester/pb/pbschema/RoleSet> <https://w3id.org/framester/pb/pbschema/hasRole> <https://w3id.org/framester/pb/pbdata/empty.01__0> <https://w3id.org/framester/pb/pbdata/empty.01__1> risorse dalla linked data cloud