Question: Which cities have more than 2 million inhabitants?
SPARQL query:
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX prop: <http://dbpedia.org/property/>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX onto: <http://dbpedia.org/ontology/>
SELECT DISTINCT ?uri ?string
WHERE 
{ 
	?uri rdf:type onto:City.
      { ?uri prop:population ?population. } 
        UNION 
      { ?uri prop:populationUrban ?population. }
	FILTER (?population > 2000000) .
	OPTIONAL {?uri rdfs:label ?string . FILTER (lang(?string) = 'en') }
}