Question: Who has been the 5th president of the United States of America?
SPARQL:
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX onto: <http://dbpedia.org/ontology/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT ?uri ?string
WHERE 
{
	?uri rdf:type onto:President .
	?uri onto:orderInOffice '5th President of the United States'@en .
        OPTIONAL {?uri rdfs:label ?string . FILTER (lang(?string) = 'en') }
}