what is the {start time} for {Robert Mueller} has {position held} as {United States Deputy Attorney General} ?
What year did Robert Muller become the US Deputy Attorney General?
When did Robert Mueller start as the United States Deputy Attorney General?
SELECT ?z WHERE { resource:Robert_Mueller property:position_held ?l . ?l property:start_time ?z . ?l property:position_held resource:United_States_Deputy_Attorney_General }
select distinct ?value  where {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q715156> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P39> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> <http://wikidata.dbpedia.org/resource/Q1364289> .
?statement <http://www.wikidata.org/entity/P580> ?value. 
} 

SELECT ?value WHERE { wd:Q715156 p:P39 ?s . ?s ps:P39 wd:Q1364289 . ?s pq:P580 ?value}