Question: What office was formerly held by Barrack Obama and is now held by an Arkansas Senator?
Answer(s):
answer: United States Senator

SPARQL query:
#MANUAL SPARQL
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
  {
    SELECT ?pFrom 
    WHERE {
      ns:m.02mjmr ns:government.politician.government_positions_held ?y . # Barack Obama 
      ?y ns:government.government_position_held.office_position_or_title ?x ; 
         ns:government.government_position_held.basic_title ns:m.060c4 ; # President
         ns:government.government_position_held.from ?pFrom .
    }
  }
  ns:m.02mjmr ns:government.politician.government_positions_held ?y . # Barack Obama 
  ?y ns:government.government_position_held.office_position_or_title ?x ; 
     ns:government.government_position_held.from ?from .
  
  FILTER(xsd:dateTime(?pFrom) - xsd:dateTime(?from) > 0)?x ns:government.government_office_or_title.office_holders ?c .
?c ns:government.government_position_held.governmental_body ns:m.09lqnv . 
}