We doubt that Lily is a frog. It is unlikely that Greg is gray. It is probably not the case that Gertrude is a wolf. It is unlikely that if 'Greg is gray and Gertrude is a wolf' then Julius is a rhino. There is a very good chance that if either 'Greg is gray' or 'Gertrude is a wolf' but not both then Brian is green. It is impossible that if 'Lily is a frog and Greg is gray' then John went to the hallway.
It is highly likely that either 'Greg is gray' or 'Lily is a frog' but not both.
It is probably not the case that either 'Greg is gray' or 'Lily is a frog' but not both.
It is highly likely that either 'Greg is gray' 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
  0.2::factA.
  0.2::factB.
  0.25::factC.
  %hop1
  0.2::factX:-and(factB,factC).
  0.8::factY:-xor(factB,factC).
  0.0::factZ:-and(factA,factB).

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

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