dawg-query-002.rq

Jena推理机

# Get names of people, together with the names of people they know.

PREFIX foaf: <http://xmlns.com/foaf/0.1/>

SELECT ?name ?name2
WHERE
  { ?person foaf:name ?name .
    OPTIONAL {
      ?person foaf:knows ?p2 .
      ?p2     foaf:name   ?name2 .
    }
  }