jena-arq/testing/DAWG-Final/boolean-effective-value/query-bev-6.rq

PREFIX  xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX  : <http://example.org/ns#>
SELECT  ?a ?w
WHERE
    { ?a :p ?v . 
      OPTIONAL
        { ?a :q ?w } . 
      FILTER ( ! ?w ) .
    }