PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> PREFIX sioc: <http://rdfs.org/sioc/ns#> PREFIX sioct: <http://rdfs.org/sioc/types#> PREFIX xsd: <http://www.w3.org/2001/XMLSchema#> PREFIX dct: <http://purl.org/dc/elements/1.1/> PREFIX dcc: <http://purl.org/dc/terms/> SELECT ?forum_name, ?post, ?title, ?link, ?cr, ?content WHERE { ?forum rdf:type sioct:Wiki . ?forum sioc:id ?forum_name. ?forum sioc:container_of ?post . ?post dct:title ?title. OPTIONAL {?post dcc:created ?cr}. OPTIONAL {?post sioc:link ?link} . OPTIONAL {?post sioc:content ?content}. }