Question: How many companies have built concrete bridges?
SPARQL query:
PREFIX res: <http://dbpedia.org/resource/>
PREFIX prop: <http://dbpedia.org/property/>
PREFIX onto: <http://dbpedia.org/ontology/>
SELECT DISTINCT COUNT(?uri) WHERE { ?x prop:material <http://dbpedia.org/resource/Concrete> . ?x onto:builder ?uri . }