SPARQL examples – negation

Find the person entries in Tim Berners-Lee’s FOAF file that do not contain a URL for the person’s FOAF file. Try this on ARQ.

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>

SELECT ?name
FROM <http://www.w3.org/People/Berners-Lee/card>
WHERE {
  ?person a foaf:Person ; foaf:name ?name .
  MINUS { ?person rdfs:seeAlso ?url }
}