#domain doors(D). boolean={true, false}. doors={1,2,3}. prize,open,selected:doors. can_open: doors -> boolean. can_open(D)=false:- selected=D. can_open(D)=false:- prize=D. can_open(D)=true:- not can_open(D)=false. [r1] random (prize). [r3] random (open:{X:can_open(X)}). [r2] random (selected). ?{prize=1,prize=2}|obs(selected=1),obs(open=2).