which material shares the same class as grey iron?
Entity Entity
m.04vtqt m.07mh3x
Ductile iron Malleable iron
class class entity
engineering.material engineering.material m.07mh2g
engineering.material engineering.material engineering.material
Material Material grey iron
none none none
engineering.material.subclass engineering.material.parent_material_class
Child material class Parent 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.07mh2g } 
?x1 :engineering.material.subclass ?x0 . 
?x2 :engineering.material.parent_material_class ?x1 . 
FILTER ( ?x0 != ?x1 && ?x0 != ?x2 && ?x1 != ?x2  )
}
}
(AND engineering.material (JOIN (R engineering.material.subclass) (JOIN (R engineering.material.parent_material_class) m.07mh2g)))