which iron material has two parent classes and what are they?
Entity Entity Entity
m.04vtqt m.07mh2g m.07mh3x
Ductile iron Gray iron Malleable iron
class class entity
engineering.material engineering.material m.025rw19
engineering.material engineering.material engineering.material
Material Material Iron
none none none
engineering.material.parent_material_class engineering.material.subclass
Parent material class Child material class
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.material . 
?x1 :type.object.type :engineering.material . 
VALUES ?x2 { :m.025rw19 } 
?x0 :engineering.material.parent_material_class ?x1 . 
?x2 :engineering.material.subclass ?x1 . 
FILTER ( ?x0 != ?x1 && ?x0 != ?x2 && ?x1 != ?x2  )
}
}
(AND engineering.material (JOIN engineering.material.parent_material_class (JOIN (R engineering.material.subclass) m.025rw19)))