Data Space Post/Entry/Item Properties (sioc:Post predicates)

   * content
   * has_container
   * has_creator
   * id
   * link
   * topic (tags)
   * links_to (TBD)
   * reply_of (TBD)
   * has_reply (TBD)

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#>
SELECT distinct ?attribute
WHERE {
        ?forum rdf:type sioct:ImageGallery.
        ?forum sioc:container_of ?post .
        ?post ?attribute ?o  
      }
ORDER BY ?attribute