There is a better than even chance that Greg is a swan. There is little chance that Mary went to the hallway. It is probably the case that John put down the milk. We believe that if either 'Greg is a swan' or 'John put down the milk' but not both then Bernhard is yellow. We doubt that if either 'Mary went to the hallway' or 'Greg is a swan' but not both then Brian is a lion. Chances are slight that if 'John put down the milk and Mary went to the hallway' then Daniel dropped the apple.
Chances are about even that either 'Brian is a lion' or 'Bernhard is yellow' but not both.
Chances are about even that either 'Brian is a lion' or 'Bernhard is yellow' but not both.
It is almost certain that either 'Brian is a lion' or 'Bernhard is yellow' 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
  0.6::factA.
  0.1::factB.
  0.7::factC.
  %hop1
  0.75::factX:-xor(factA,factC).
  0.2::factY:-xor(factB,factA).
  0.1::factZ:-and(factC,factB).

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

  query(conclusion).
  
Either 'Brian is a lion' or 'Bernhard is yellow' but not both.