We doubt that Bernhard is a frog. There is a better than even chance that Daniel dropped the apple. We believe that Mary went to the hallway. There is almost no chance that if 'Bernhard is a frog and Mary went to the hallway' then Gertrude is a sheep. It is almost certain that if either 'Bernhard is a frog' or 'Daniel dropped the apple' but not both then Julius is a swan. It is almost certain that if 'Bernhard is a frog and Mary went to the hallway' then Brian is gray.
It is improbable that either 'Daniel dropped the apple' or 'Bernhard is a frog' but not both.
There is a better than even chance that either 'Daniel dropped the apple' or 'Bernhard is a frog' but not both.
It is improbable that either 'Daniel dropped the apple' or 'Bernhard is a frog' 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
  0.2::factA.
  0.6::factB.
  0.75::factC.
  %hop1
  0.02::factX:-and(factA,factC).
  0.95::factY:-xor(factA,factB).
  0.95::factZ:-and(factA,factC).

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

  query(conclusion).
  
Either 'Daniel dropped the apple' or 'Bernhard is a frog' but not both.