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

   * content
   * has_container
   * has_creator
   * id
   * link
   * links_to
   * topic (tags) 
   * has_reply (TBD)
   * reply_of  (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 sioc:Community .
    ?forum sioc:has_part ?parentf .
    ?parentf sioc:container_of ?post .
    ?post ?attribute ?o
  }
ORDER BY ?attribute