It is almost certain that Bernhard is a swan. It is highly likely that Mary went to the bedroom. It is highly unlikely that Brian is green. It is highly likely that if either 'Brian is green' or 'Bernhard is a swan' but not both then Yann is bored. There is almost no chance that if either 'Bernhard is a swan' or 'Brian is green' but not both then Fred dropped the milk. We believe that if 'Brian is green' or 'Bernhard is a swan' or both then Greg is a rhino.
There is little chance that either 'Fred dropped the milk' or 'Greg is a rhino' but not both.
It is likely that either 'Fred dropped the milk' or 'Greg is a rhino' but not both.
There is little chance that either 'Fred dropped the milk' or 'Greg is a rhino' 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
  0.95::factA.
  0.9::factB.
  0.05::factC.
  %hop1
  0.9::factX:-xor(factC,factA).
  0.02::factY:-xor(factA,factC).
  0.75::factZ:-or(factC,factA).

  %hop2
  conclusion:-xor(factY,factZ).

  query(conclusion).
  
Either 'Fred dropped the milk' or 'Greg is a rhino' but not both.