It is impossible that Julius is a lion. It is highly likely that Mary got the football. It is impossible that Gertrude is a mouse. We believe that if either 'Gertrude is a mouse' or 'Julius is a lion' but not both then John picked up the apple. It is almost certain that if either 'Mary got the football' or 'Julius is a lion' but not both then Lily is a rhino. It is unlikely that if 'Mary got the football and Gertrude is a mouse' then Brian is yellow.
It is certain that either 'Julius is a lion' or 'John picked up the apple' but not both.
It is impossible that either 'Julius is a lion' or 'John picked up the apple' but not both.
It is certain that either 'Julius is a lion' or 'John picked up the apple' 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
  0.0::factA.
  0.9::factB.
  0.0::factC.
  %hop1
  0.75::factX:-xor(factC,factA).
  0.95::factY:-xor(factB,factA).
  0.2::factZ:-and(factB,factC).

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

  query(conclusion).
  
Either 'Julius is a lion' or 'John picked up the apple' but not both.