Question: Which politician's constituency is led by the SF Board of Supervisors?
SPARQL query:
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX prop: <http://dbpedia.org/property/>
PREFIX onto: <http://dbpedia.org/ontology/>
SELECT DISTINCT ?uri WHERE { ?x prop:leaderTitle <http://dbpedia.org/resource/San_Francisco_Board_of_Supervisors> . ?uri prop:constituency ?x  . ?uri rdf:type onto:OfficeHolder}