There is almost no chance that Brian is a frog. There is little chance that Bernhard is gray. It is probably not the case that Julius is a swan. Chances are slight that if 'Bernhard is gray' or 'Julius is a swan' or both then Greg is a rhino. It is likely that if either 'Bernhard is gray' or 'Brian is a frog' but not both then John took the apple. It is highly unlikely that if 'Bernhard is gray' or 'Julius is a swan' or both then Sandra grabbed the milk.
It is highly likely that either 'Sandra grabbed the milk' or 'Julius is a swan' but not both.
It is probably not the case that either 'Sandra grabbed the milk' or 'Julius is a swan' but not both.
It is highly likely that either 'Sandra grabbed the milk' or 'Julius is a swan' 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
  0.02::factA.
  0.1::factB.
  0.25::factC.
  %hop1
  0.1::factX:-or(factB,factC).
  0.7::factY:-xor(factB,factA).
  0.05::factZ:-or(factB,factC).

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

  query(conclusion).
  
Either 'Sandra grabbed the milk' or 'Julius is a swan' but not both.