title: SPARQL DESCRIBE query
body: <p>Seems I don't grok SPARQL DESCRIBE queries. I need to retrieve the full graphs of resources matching a condition. On one SPARQL endpoint I have tried (Norwegian Rådata Nå, <a href="http://data.bibsys.no/data/query_authority.html" rel="nofollow noreferrer">http://data.bibsys.no/data/query_authority.html</a>) this works just fine:</p>
  
  <pre><code>PREFIX foaf: &lt;http://xmlns.com/foaf/0.1/&gt; 
  PREFIX rdf: &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt;
  PREFIX owl: &lt;http://www.w3.org/2002/07/owl#&gt;
  
  DESCRIBE ?person WHERE {
    ?person rdf:type foaf:Person .
    FILTER EXISTS { ?person owl:sameAs ?sameAs }
  }
  LIMIT 100
  </code></pre>
  
  <p>I get a result with Person resources that have an <code>owl:sameAs</code> triple.</p>
  
  <p>On other SPARQL endpoints, Onki Light (<a href="http://sparql.onki.fi/sparql.tpl" rel="nofollow noreferrer">http://sparql.onki.fi/sparql.tpl</a>) and DBPedia (<a href="http://dbpedia.org/sparql" rel="nofollow noreferrer">http://dbpedia.org/sparql</a>) a similar query</p>
  
  <pre><code>PREFIX rdf: &lt;http://www.w3.org/1999/02/22-rdf-syntax-ns#&gt;
  PREFIX skos: &lt;http://www.w3.org/2004/02/skos/core#&gt;
  
  DESCRIBE ?x WHERE {
    ?x rdf:type skos:Concept .
    FILTER EXISTS { ?x skos:prefLabel ?prefLabel }
  }
  LIMIT 100
  </code></pre>
  
  <p>returns lots of resources which have neither <code>rdf:Type = skos:Concept</code> nor a <code>skos:prefLabel</code>, so I am obviously not doing the query correctly. How should this kind of query be stated to produce the result I need?</p>