Question: Which coach of the Carolina Panthers has their roster position as defensive back?
Answer(s):
answer: John Fox

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.01y3c)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.01y3c ns:american_football.football_team.historical_coaching_staff ?y .
?y ns:american_football.football_historical_coach_position.coach ?x .
?x ns:sports.pro_athlete.teams ?c .
?c ns:sports.sports_team_roster.position ns:m.01_9c1 . 
}