Question: Who was the successor of John F. Kennedy?
SPARQL:
PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX res: <http://dbpedia.org/resource/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT DISTINCT ?uri ?string WHERE 
{
	res:John_F._Kennedy dbo:successor ?uri .
        OPTIONAL { ?uri rdfs:label ?string. FILTER (lang(?string) = 'en') }
}