Question: What are some party leaders of the parties which have had a seat in Berlin?
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:headquarter <http://dbpedia.org/resource/Berlin> . ?x onto:leader ?uri  . ?x rdf:type onto:PoliticalParty}