It is probably not the case that Gertrude is a mouse. It is impossible that Julius is a lion. It is highly unlikely that Lily is yellow. It is improbable that if 'Lily is yellow and Gertrude is a mouse' then Bernhard is a swan. It is certain that if 'Lily is yellow and Gertrude is a mouse' then Brian is a frog. There is a better than even chance that if either 'Julius is a lion' or 'Gertrude is a mouse' but not both then John took the apple.
It is almost certain that either 'Brian is a frog' or 'Julius is a lion' but not both.
There is almost no chance that either 'Brian is a frog' or 'Julius is a lion' but not both.
It is almost certain that either 'Brian is a frog' 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
  0.25::factA.
  0.0::factB.
  0.05::factC.
  %hop1
  0.1::factX:-and(factC,factA).
  1.0::factY:-and(factC,factA).
  0.6::factZ:-xor(factB,factA).

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

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