title: Datatype result SPARQL query in Jena
body: <p>I've a problem in results of my sparql query.
  This is my query :</p>
  
  <pre><code>String queryBody = "REGISTER QUERY noreasoning AS "
                      + "PREFIX ds:&lt;http://www.dati.lombardia.it/resource/nf78-nj6b/&gt; "
  
                      + "SELECT   ?idSensore ?valoreMisurazione ?tipologia ?nomeComune "
  
                      + "FROM STREAM &lt;http://streamreasoning.org/streams/sensors&gt; [RANGE 10s STEP 1s] "
                      + "FROM &lt;http://streamreasoning.org/roomConnection&gt; "                   
  
                      + "WHERE { "
  
                      + "?s ds:idsensore ?idSensore. "
                      + "?s ds:observes ?valoreMisurazione. "
                      + "?s ds:tipologia ?tipologia. "
                      + "?s ds:nomecomune ?nomeComune. "
                      +"  FILTER ( datatype(?tipologia) = xds:langString)\n"
  
                      + "} ";     
  </code></pre>
  
  <p>and my result is this:</p>
  
  <pre><code>-------3 results at SystemTime=[1464188665959]--------
  "2447"^^null    6   "Temperatura"^^null "Bema"^^null    
  "8016"^^null    -1.3    "Temperatura"^^null "Aprica"^^null  
  "4066"^^null    7.9 "Temperatura"^^null "Arconate"^^null
  </code></pre>
  
  <p>What should I change to remove "^^null"?</p>