There is little chance that Yann is hungry. There is little chance that Lily is a frog. It is almost certain that John went to the garden. There is little chance that if 'Yann is hungry and Lily is a frog' then Mary dropped the milk. Chances are slight that if either 'Yann is hungry' or 'John went to the garden' but not both then Brian is a lion. There is a very good chance that if 'Lily is a frog and John went to the garden' then Julius is white.
We doubt that either 'Brian is a lion' or 'Lily is a frog' but not both.
We doubt that either 'Brian is a lion' or 'Lily is a frog' but not both.
It is probable that either 'Brian is a lion' or 'Lily is a frog' 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
  0.1::factA.
  0.1::factB.
  0.95::factC.
  %hop1
  0.1::factX:-and(factA,factB).
  0.1::factY:-xor(factA,factC).
  0.8::factZ:-and(factB,factC).

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

  query(conclusion).
  
Either 'Brian is a lion' or 'Lily is a frog' but not both.