# Get names and mboxes, each of which may be optional.

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#>

SELECT ?name ?mbox
WHERE
  {
    { ?person rdf:type foaf:Person } .
    OPTIONAL { ?person foaf:name  ?name } .
    OPTIONAL { ?person foaf:mbox  ?mbox } .
  }