what opera genre is the genre of an opera whose date of first performance is before 04/15/1738?
Entity Entity
m.01_22_ m.04dg7h2
Opera seria Opera in three acts
class class literal
opera.opera_genre opera.opera 1738-04-15^^http://www.w3.org/2001/XMLSchema#date
opera.opera_genre opera.opera type.datetime
Opera Genre Opera 04/15/1738
none none <
opera.opera.genre music.composition.date_of_first_performance
Genre Date of first performance
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> PREFIX : <http://rdf.freebase.com/ns/> 
SELECT (?x0 AS ?value) WHERE {
SELECT DISTINCT ?x0  WHERE { 
?x0 :type.object.type :opera.opera_genre . 
?x1 :type.object.type :opera.opera . 
FILTER (?x2 < "1738-04-15-08:00"^^<http://www.w3.org/2001/XMLSchema#date>)
?x1 :opera.opera.genre ?x0 . 
?x1 :music.composition.date_of_first_performance ?x2 . 
FILTER ( ?x0 != ?x1 && ?x0 != ?x2 && ?x1 != ?x2  )
}
}
(AND opera.opera_genre (JOIN (R opera.opera.genre) (lt music.composition.date_of_first_performance 1738-04-15^^http://www.w3.org/2001/XMLSchema#date)))