It is probable that Gertrude is a mouse. It is impossible that Greg is a rhino. It is impossible that Brian is a swan. Chances are slight that if either 'Gertrude is a mouse' or 'Greg is a rhino' but not both then Mary is in the bathroom. We doubt that if either 'Greg is a rhino' or 'Gertrude is a mouse' but not both then John left the football. We believe that if 'Gertrude is a mouse' or 'Greg is a rhino' or both then Bernhard is yellow.
There is little chance that either 'Gertrude is a mouse' or 'Mary is in the bathroom' but not both.
There is a better than even chance that either 'Gertrude is a mouse' or 'Mary is in the bathroom' but not both.
There is little chance that either 'Gertrude is a mouse' or 'Mary is in the bathroom' but not both.

  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.
  0.0::factB.
  0.0::factC.
  %hop1
  0.1::factX:-xor(factA,factB).
  0.2::factY:-xor(factB,factA).
  0.75::factZ:-or(factA,factB).

  %hop2
  conclusion:-xor(factA,factX).

  query(conclusion).
  
Either 'Gertrude is a mouse' or 'Mary is in the bathroom' but not both.