We believe that John moved to the garden. There is little chance that Gertrude is a sheep. It is likely that Lily is a swan. We doubt that if either 'Gertrude is a sheep' or 'Lily is a swan' but not both then Mary took the milk. It is improbable that if either 'Lily is a swan' or 'Gertrude is a sheep' but not both then Brian is a frog. It is highly likely that if either 'John moved to the garden' or 'Lily is a swan' but not both then Julius is green.
It is probably not the case that either 'Lily is a swan' or 'Gertrude is a sheep' but not both.
It is probably the case that either 'Lily is a swan' or 'Gertrude is a sheep' but not both.
It is probably not the case that either 'Lily is a swan' or 'Gertrude is a sheep' 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.
  0.1::factB.
  0.7::factC.
  %hop1
  0.2::factX:-xor(factB,factC).
  0.1::factY:-xor(factC,factB).
  0.9::factZ:-xor(factA,factC).

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

  query(conclusion).
  
Either 'Lily is a swan' or 'Gertrude is a sheep' but not both.