Question: When was Hartmut Mehdorn appointed a director at Deutsche Bahn?
Paraphrase: Harmut Mehdorn became director at Deutsche Bahn when?
SPARQL (Wikidata): SELECT ?value WHERE { wd:Q9322 p:P1037 ?s . ?s ps:P1037 wd:Q91984 . ?s pq:P580 ?value}