---+++Wikiword Tags 
<verbatim>
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 skos: <http://www.w3.org/2004/02/skos/core#>
SELECT DISTINCT ?tag ?topic
WHERE 
  {
    ?forum a sioct:Wiki .
    ?forum sioc:container_of ?post.
    optional{ ?post sioc:topic ?topic .
                  ?topic rdf:type skos:Concept .
                  ?topic skos:prefLabel ?tag }
   }
</verbatim>

---+++++Sample Data (Live Query Results)
   * Click [[http://demo.openlinksw.com/sparql?default-graph-uri=http%3A%2F%2Fdemo.openlinksw.com%2Fdataspace&should-sponge=&query=PREFIX+rdf%3A+%3Chttp%3A%2F%2Fwww.w3.org%2F1999%2F02%2F22-rdf-syntax-ns%23%3E%0D%0APREFIX+sioc%3A+%3Chttp%3A%2F%2Frdfs.org%2Fsioc%2Fns%23%3E%0D%0APREFIX+sioct%3A+%3Chttp%3A%2F%2Frdfs.org%2Fsioc%2Ftypes%23%3E%0D%0APREFIX+skos%3A+%3Chttp%3A%2F%2Fwww.w3.org%2F2004%2F02%2Fskos%2Fcore%23%3E%0D%0ASELECT+DISTINCT+%3Ftag+%3Ftopic%0D%0AWHERE+%0D%0A++%7B%0D%0A++++%3Fforum+a+sioct%3AWiki+.%0D%0A++++%3Fforum+sioc%3Acontainer_of+%3Fpost.%0D%0A++++optional%7B+%3Fpost+sioc%3Atopic+%3Ftopic+.%0D%0A++++++++++++++++++%3Ftopic+rdf%3Atype+skos%3AConcept+.%0D%0A++++++++++++++++++%3Ftopic+skos%3AprefLabel+%3Ftag+%7D%0D%0A+++%7D&format=text%2Fhtml][Here]] for a live SPARQL Query (via SPARQL Protocol) against a Collection of Wikis tags.