Question: What is the name of the mother of Prince, the music producer who produced "Sometimes Late at Night?"?
Answer(s):
answer: Katherine Jackson

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ?c)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
?c ns:music.producer.releases_produced ns:m.0bfkkg7 . 
?c ns:people.person.parents ?x .
?x ns:people.person.gender ns:m.02zsn .
}