We doubt that Julius is white. It is probably the case that Winona is a wolf. It is highly likely that Greg is gray. It is highly unlikely that if 'Greg is gray and Winona is a wolf' then John moved to the office. Chances are about even that if 'Greg is gray' or 'Winona is a wolf' or both then Bernhard is a lion. It is unlikely that if either 'Julius is white' or 'Greg is gray' but not both then Lily is a frog.
It is improbable that either 'Lily is a frog' or 'Greg is gray' but not both.
We believe that either 'Lily is a frog' or 'Greg is gray' but not both.
It is improbable that either 'Lily is a frog' or 'Greg is gray' 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
  0.2::factA.
  0.7::factB.
  0.9::factC.
  %hop1
  0.05::factX:-and(factC,factB).
  0.5::factY:-or(factC,factB).
  0.2::factZ:-xor(factA,factC).

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

  query(conclusion).
  
Either 'Lily is a frog' or 'Greg is gray' but not both.