Question: List presidents of the school whose one of the president is Charles. Prince of Wales ?
SPARQL:
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/ontology/president> <http://dbpedia.org/resource/Charles,_Prince_of_Wales> . ?x <http://dbpedia.org/property/president> ?uri  . ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/School>}