which rail gauges correspond with british rail class 50 class?
Entity
m.075hw
Standard gauge
class entity
rail.rail_gauge m.052dz1
rail.rail_gauge rail.locomotive_class
Rail gauge British Rail Class 50
none none
rail.rail_gauge.locomotive_classes
Locomotive classes
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 :rail.rail_gauge . 
VALUES ?x1 { :m.052dz1 } 
?x0 :rail.rail_gauge.locomotive_classes ?x1 . 
FILTER ( ?x0 != ?x1  )
}
}
(AND rail.rail_gauge (JOIN rail.rail_gauge.locomotive_classes m.052dz1))