It is probably not the case that Daniel grabbed the milk. There is little chance that Mary went to the bedroom. There is almost no chance that Greg is a rhino. There is a better than even chance that if either 'Mary went to the bedroom' or 'Daniel grabbed the milk' but not both then Bernhard is white. It is probable that if 'Greg is a rhino' or 'Mary went to the bedroom' or both then Gertrude is a mouse. It is unlikely that if either 'Mary went to the bedroom' or 'Daniel grabbed the milk' but not both then Bill left the football.
We doubt that either 'Bernhard is white' or 'Daniel grabbed the milk' but not both.
We doubt that either 'Bernhard is white' or 'Daniel grabbed the milk' but not both.
It is probable that either 'Bernhard is white' or 'Daniel grabbed the milk' 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
  0.25::factA.
  0.1::factB.
  0.02::factC.
  %hop1
  0.6::factX:-xor(factB,factA).
  0.7::factY:-or(factC,factB).
  0.2::factZ:-xor(factB,factA).

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

  query(conclusion).
  
Either 'Bernhard is white' or 'Daniel grabbed the milk' but not both.