title: How to filter the simple Subject in a SPARQL Query
body: <p>I guess I am stuck at the basics with SPARQL. Can someone help ?</p>
  
  <p>I simply wnat to filter all subjects containing "Mountain" of an RDS database.</p>
  
  <pre><code>Prefix lgdr:&lt;http://linkedgeodata.org/triplify/&gt; Prefix lgdo:&lt;http://linkedgeodata.org/ontology/&gt; 
  Select * where { 
  ?s ?p ?o . 
  filter (contains(?s, "Mountain"))
  } Limit 1000
  </code></pre>
  
  <p>The query leads to an error:</p>
  
  <pre><code>Virtuoso 22023 Error SL001: The SPARQL 1.1 function CONTAINS() needs a string value as first argument
  </code></pre>