There is a better than even chance that John dropped the apple. There is a better than even chance that Bernhard is a lion. It is probable that Julius is a swan. It is unlikely that if 'Julius is a swan and Bernhard is a lion' then Mary went to the bedroom. It is improbable that if either 'Bernhard is a lion' or 'John dropped the apple' but not both then Brian is a frog. There is a very good chance that if either 'John dropped the apple' or 'Julius is a swan' but not both then Lily is a rhino.
It is certain that either 'Julius is a swan' or 'Bernhard is a lion' but not both.
Chances are about even that either 'Julius is a swan' or 'Bernhard is a lion' but not both.
It is certain that either 'Julius is a swan' or 'Bernhard 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
  0.6::factA.
  0.6::factB.
  0.7::factC.
  %hop1
  0.2::factX:-and(factC,factB).
  0.1::factY:-xor(factB,factA).
  0.8::factZ:-xor(factA,factC).

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

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