Question: Who produces the trains operated by the MTR?
SPARQL query:
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX onto: <http://dbpedia.org/ontology/>
SELECT DISTINCT ?uri WHERE { ?x onto:operator <http://dbpedia.org/resource/MTR> . ?x onto:manufacturer ?uri . ?x rdf:type onto:Train}