It is highly likely that Mary got the football. We believe that Greg is a lion. Chances are slight that Julius is gray. It is almost certain that if 'Julius is gray and Greg is a lion' then Yann is hungry. It is improbable that if 'Greg is a lion' or 'Julius is gray' or both then Brian is a lion. It is highly unlikely that if 'Julius is gray' or 'Mary got the football' or both then John went to the kitchen.
It is certain that either 'Brian is a lion' or 'John went to the kitchen' but not both.
Chances are slight that either 'Brian is a lion' or 'John went to the kitchen' but not both.
It is certain that either 'Brian is a lion' or 'John went to the kitchen' 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
  0.9::factA.
  0.75::factB.
  0.1::factC.
  %hop1
  0.95::factX:-and(factC,factB).
  0.1::factY:-or(factB,factC).
  0.05::factZ:-or(factC,factA).

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

  query(conclusion).
  
Either 'Brian is a lion' or 'John went to the kitchen' but not both.