We doubt that Julius is a lion. We believe that Gertrude is a cat. It is unlikely that John dropped the apple. We believe that if 'John dropped the apple and Julius is a lion' then Lily is a rhino. Chances are about even that if either 'Julius is a lion' or 'Gertrude is a cat' but not both then Emily is a cat. It is likely that if either 'Julius is a lion' or 'John dropped the apple' but not both then Bernhard is a rhino.
We believe that either 'Bernhard is a rhino' or 'Julius is a lion' but not both.
It is unlikely that either 'Bernhard is a rhino' or 'Julius is a lion' but not both.
We believe that either 'Bernhard is a rhino' or 'Julius is a lion' 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.
  0.75::factB.
  0.2::factC.
  %hop1
  0.75::factX:-and(factC,factA).
  0.5::factY:-xor(factA,factB).
  0.7::factZ:-xor(factA,factC).

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

  query(conclusion).
  
Either 'Bernhard is a rhino' or 'Julius is a lion' but not both.