PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> 
PREFIX sioc: <http://rdfs.org/sioc/ns#> 
PREFIX rss: <http://purl.org/rss/1.0/>
PREFIX dc: <http://purl.org/dc/elements/1.1/>

CONSTRUCT {
  ?channel rdf:type sioc:Forum .
  ?channel sioc:link ?channel_url .
  ?channel dc:title ?channel_title .
  ?channel dc:description ?channel_description .
  ?channel sioc:container_of ?item .
  ?item rdf:type sioc:Post .
  ?item sioc:link ?item_url .
  ?item dc:title ?item_title .
  ?item sioc:content ?item_content .
}
WHERE {
  ?channel rdf:type rss:channel .
  ?channel rss:link ?channel_url .
  ?channel rss:title ?channel_title .
  ?channel rss:description ?channel_description .
  ?channel rss:items ?items .
  ?items ?li ?item .
  ?item rdf:type rss:item .
  ?item rss:link ?item_url .
  ?item rss:title ?item_title .
  ?item rss:description ?item_content .
}