1% false.
    2% Contradiction: OLON rule forces q to be false, fact forces it to be true.
    3
    4p :- q, not p.
    5q.
    6
    7_out :- p.
    8_out :- q.
    9_out :- not p.
   10_out :- not q.
   11
   12% #compute 1 { _out }.
   13:- not