Question: What is the sea whose cities are Gdask and Oulu?
SPARQL:
SELECT DISTINCT ?uri WHERE { ?uri <http://dbpedia.org/property/cities> <http://dbpedia.org/resource/Gdańsk> . ?uri <http://dbpedia.org/property/cities> <http://dbpedia.org/resource/Oulu> . ?uri <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Sea>}