Wiki articles creator nick and organization details

PREFIX sioc: <http://rdfs.org/sioc/ns#>
PREFIX sioct: <http://rdfs.org/sioc/types#>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
CONSTRUCT
  {
    ?post foaf:maker ?maker .
    ?maker foaf:nick ?nick  .
    ?maker foaf:organization ?org  .
  }
WHERE 
  {
    ?forum a sioct:Wiki .
    ?forum sioc:container_of ?post.
    optional { ?post foaf:maker ?maker }.
    optional { ?maker foaf:nick ?nick  } .
    optional { ?maker foaf:organization ?org } .
  }