Question: Give me all presidents of the United States.
SPARQL:
PREFIX yago: <http://dbpedia.org/class/yago/>
PREFIX dbo: <http://dbpedia.org/ontology/>
PREFIX dbp: <http://dbpedia.org/property/>
PREFIX res: <http://dbpedia.org/resource/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT DISTINCT ?uri ?string 
WHERE {
        ?uri rdf:type dbo:Person .
        { ?uri rdf:type yago:PresidentsOfTheUnitedStates. }
        UNION
        { ?uri rdf:type dbo:President.
          ?uri dbp:title res:President_of_the_United_States. }
        ?uri rdfs:label ?string. 
        FILTER (lang(?string) = 'en' && !regex(?string,'Presidency','i') && !regex(?string,'and the')) .
}