We believe that Brian is a rhino. Chances are slight that Julius is a frog. It is unlikely that Sandra left the apple. It is probably not the case that if either 'Sandra left the apple' or 'Julius is a frog' but not both then John went to the hallway. We doubt that if 'Julius is a frog and Sandra left the apple' then Bernhard is white. It is probable that if 'Sandra left the apple' or 'Brian is a rhino' or both then Mary got the milk.
We believe that either 'Julius is a frog' or 'John went to the hallway' but not both.
Chances are slight that either 'Julius is a frog' or 'John went to the hallway' but not both.
We believe that either 'Julius is a frog' or 'John went to the hallway' 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
  0.75::factA.
  0.1::factB.
  0.2::factC.
  %hop1
  0.25::factX:-xor(factC,factB).
  0.2::factY:-and(factB,factC).
  0.7::factZ:-or(factC,factA).

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

  query(conclusion).
  
Either 'Julius is a frog' or 'John went to the hallway' but not both.