PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> PREFIX atom: <http://atomowl.org/ontologies/atomrdf#> PREFIX sioc: <http://rdfs.org/sioc/ns#> PREFIX sioct: <http://rdfs.org/sioc/types#> SELECT DISTINCT ?post, ?title WHERE { ?forum a sioct:BookmarkFolder . ?forum sioc:container_of ?post. optional {?post atom:title ?title }. }