Question: What is an exhibition venue in Philadelphia that opened on May 21, 1989 ?
Answer(s):
answer: Philadelphia Museum of Art

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.0dclg)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.0dclg ns:travel.travel_destination.tourist_attractions ?x .
?x ns:exhibitions.exhibition_venue.exhibitions_at_this_venue ?c .
?c ns:exhibitions.exhibition_run.opened_on "1989-05-21"^^xsd:dateTime . 
}