We believe that Lily is a frog. It is certain that Greg is a swan. It is unlikely that Daniel grabbed the milk. We doubt that if 'Lily is a frog' or 'Daniel grabbed the milk' or both then Bernhard is green. It is impossible that if either 'Lily is a frog' or 'Greg is a swan' but not both then John went to the kitchen. It is impossible that if either 'Daniel grabbed the milk' or 'Lily is a frog' but not both then Mary left the apple.
There is almost no chance that either 'Bernhard is green' or 'Lily is a frog' but not both.
There is a better than even chance that either 'Bernhard is green' or 'Lily is a frog' but not both.
There is almost no chance that either 'Bernhard is green' or 'Lily is a frog' 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
  0.75::factA.
  1.0::factB.
  0.2::factC.
  %hop1
  0.2::factX:-or(factA,factC).
  0.0::factY:-xor(factA,factB).
  0.0::factZ:-xor(factC,factA).

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

  query(conclusion).
  
Either 'Bernhard is green' or 'Lily is a frog' but not both.