Question: What is that river whose source gets water from the Shannon cave?
SPARQL:
SELECT DISTINCT ?uri WHERE { ?x <http://dbpedia.org/property/inflow> <http://dbpedia.org/resource/Shannon_Cave> . ?uri <http://dbpedia.org/ontology/source> ?x  . ?uri <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/River>}