Question: What is the ruling party in Lisbon?
SPARQL:
PREFIX dbp: <http://dbpedia.org/property/>
PREFIX res: <http://dbpedia.org/resource/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT DISTINCT ?uri ?string WHERE 
{
	res:Lisbon dbp:leaderParty ?uri .
	OPTIONAL { ?uri rdfs:label ?string. FILTER (lang(?string) = 'en') }
}