Question: Who sang for Pink Floyd, who's date of death is before Sept 15, 2008?
Answer(s):
answer: Syd Barrett

SPARQL query:
#MANUAL SPARQL
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
  {
    ns:m.01wv9xn ns:music.musical_group.member ?y .
    ?y ns:music.group_membership.member ?x ;
       ns:music.group_membership.role ns:m.0290ngj . #vocals
  }
  UNION
  {
    ns:m.01wv9xn ns:music.musical_group.member ?y .
    ?y ns:music.group_membership.member ?x ;
       ns:music.group_membership.role ns:m.0_sv_90 . #lead vocals
  }?x ns:people.deceased_person.date_of_death ?num .
FILTER (?num < "2008-09-15"^^xsd:dateTime) . 
}