There is little chance that Winona is a cat. Chances are slight that Julius is a frog. It is certain that Brian is white. It is improbable that if either 'Winona is a cat' or 'Brian is white' but not both then Sandra dropped the milk. It is probably the case that if 'Brian is white' or 'Julius is a frog' or both then Bernhard is yellow. It is probably the case that if 'Brian is white and Winona is a cat' then Mary moved to the office.
We believe that either 'Julius is a frog' or 'Winona is a cat' but not both.
It is unlikely that either 'Julius is a frog' or 'Winona is a cat' but not both.
We believe that either 'Julius is a frog' or 'Winona is a cat' 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
  0.1::factA.
  0.1::factB.
  1.0::factC.
  %hop1
  0.1::factX:-xor(factA,factC).
  0.7::factY:-or(factC,factB).
  0.7::factZ:-and(factC,factA).

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

  query(conclusion).
  
Either 'Julius is a frog' or 'Winona is a cat' but not both.