what is the piston configuration of the rolls-royce merlin i?
Entity
m.0800_
V12 engine
class class entity
engineering.piston_configuration engineering.piston_engine m.07_29vt
engineering.piston_configuration engineering.piston_engine engineering.piston_engine
Piston configuration Piston engine Rolls-Royce Merlin I
none none none
engineering.piston_engine.piston_configuration engineering.engine.variation_of
Piston configuration Variation of
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 :engineering.piston_configuration . 
?x1 :type.object.type :engineering.piston_engine . 
VALUES ?x2 { :m.07_29vt } 
?x1 :engineering.piston_engine.piston_configuration ?x0 . 
?x2 :engineering.engine.variation_of ?x1 . 
FILTER ( ?x0 != ?x1 && ?x0 != ?x2 && ?x1 != ?x2  )
}
}
(AND engineering.piston_configuration (JOIN (R engineering.piston_engine.piston_configuration) (JOIN (R engineering.engine.variation_of) m.07_29vt)))