Chances are slight that John moved to the garden. Chances are slight that Mary discarded the milk. It is certain that Julius is a frog. There is almost no chance that if 'Mary discarded the milk and John moved to the garden' then Bernhard is white. It is almost certain that if either 'Julius is a frog' or 'John moved to the garden' but not both then Brian is a rhino. There is little chance that if 'Mary discarded the milk and John moved to the garden' then Fred left the apple.
There is a very good chance that either 'Brian is a rhino' or 'Mary discarded the milk' but not both.
There is a very good chance that either 'Brian is a rhino' or 'Mary discarded the milk' but not both.
Chances are slight that either 'Brian is a rhino' or 'Mary 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
  0.1::factA.
  0.1::factB.
  1.0::factC.
  %hop1
  0.02::factX:-and(factB,factA).
  0.95::factY:-xor(factC,factA).
  0.1::factZ:-and(factB,factA).

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

  query(conclusion).
  
Either 'Brian is a rhino' or 'Mary discarded the milk' but not both.