It is probably not the case that Mary dropped the milk. Chances are about even that Winona is a wolf. It is probably not the case that Daniel took the apple. It is likely that if 'Winona is a wolf and Daniel took the apple' then John moved to the garden. It is certain that if either 'Daniel took the apple' or 'Winona is a wolf' but not both then Brian is a rhino. There is a better than even chance that if 'Mary dropped the milk and Daniel took the apple' then Greg is green.
It is improbable that either 'Brian is a rhino' or 'John moved to the garden' but not both.
There is a better than even chance that either 'Brian is a rhino' or 'John moved to the garden' but not both.
It is improbable that either 'Brian is a rhino' or 'John moved to the garden' 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.
  0.5::factB.
  0.25::factC.
  %hop1
  0.7::factX:-and(factB,factC).
  1.0::factY:-xor(factC,factB).
  0.6::factZ:-and(factA,factC).

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

  query(conclusion).
  
Either 'Brian is a rhino' or 'John moved to the garden' but not both.