1% { q, s, not p, not r }
    2% for ?- q, s. : { q, not p, s, not r }
    3
    4p :- not q.
    5q :- not p.
    6r :- not s.
    7s :- not r.
    8
    9% #compute 1 {q,s}.
   10comp :- q, s.
   11:- not comp.