# https://www.w3.org/TR/sparql11-federated-query/

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

SELECT ?name
FROM <http://example.org/myfoaf.rdf>
WHERE
{
  <http://example.org/myfoaf/I> foaf:knows ?person .
  SERVICE <http://people.example.org/sparql> {
    ?person foaf:name ?name . }
}
# Error message: Unknown namespace prefix : foaf
