Chances are about even that Brian is green. There is a better than even chance that Mary went to the bedroom. Chances are about even that Julius is white. We believe that if either 'Julius is white' or 'Mary went to the bedroom' but not both then Jessica is a mouse. It is almost certain that if either 'Brian is green' or 'Julius is white' but not both then John discarded the milk. It is highly unlikely that if either 'Julius is white' or 'Brian is green' but not both then Bernhard is a swan.
Chances are about even that either 'Julius is white' or 'John discarded the milk' but not both.
Chances are about even that either 'Julius is white' or 'John discarded the milk' but not both.
It is almost certain that either 'Julius is white' or 'John discarded 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
  0.5::factA.
  0.6::factB.
  0.5::factC.
  %hop1
  0.75::factX:-xor(factC,factB).
  0.95::factY:-xor(factA,factC).
  0.05::factZ:-xor(factC,factA).

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

  query(conclusion).
  
Either 'Julius is white' or 'John discarded the milk' but not both.