Question: How many labels sign up progressive rock artists?
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:genre <http://dbpedia.org/resource/Progressive_rock> . ?x onto:recordLabel ?uri . }