It is probably the case that Mary went to the bedroom. We believe that Greg is white. There is little chance that Gertrude is a wolf. Chances are slight that if either 'Gertrude is a wolf' or 'Greg is white' but not both then Bernhard is green. It is improbable that if 'Gertrude is a wolf' or 'Mary went to the bedroom' or both then John dropped the apple. There is almost no chance that if 'Greg is white and Mary went to the bedroom' then Lily is a lion.
There is a very good chance that 'Gertrude is a wolf and Bernhard is green'.
It is impossible that 'Gertrude is a wolf and Bernhard is green'.
There is a very good chance that 'Gertrude is a wolf and Bernhard is green'.

  and(A,B) :- A,B.
  or(A,B) :- A;B.
  nand(A,B) :- not(and(A,B)).
  nor(A,B) :- not(or(A,B)).
  xor(A,B) :- or(A,B), nand(A,B).

  %hop0
  0.7::factA.
  0.75::factB.
  0.1::factC.
  %hop1
  0.1::factX:-xor(factC,factB).
  0.1::factY:-or(factC,factA).
  0.02::factZ:-and(factB,factA).

  %hop2
  conclusion:-and(factC,factX).

  query(conclusion).
  
'Gertrude is a wolf and Bernhard is green'.