Chances are about even that Greg is gray. There is a very good chance that Winona is a wolf. It is probably the case that John went to the kitchen. It is almost certain that if 'Winona is a wolf and John went to the kitchen' then Gertrude is a mouse. It is improbable that if 'Greg is gray' or 'John went to the kitchen' or both then Lily is a swan. There is little chance that if 'John went to the kitchen' or 'Greg is gray' or both then Mary dropped the apple.
Chances are about even that either 'Winona is a wolf' or 'Greg is gray' but not both.
Chances are about even that either 'Winona is a wolf' or 'Greg is gray' but not both.
It is highly unlikely that either 'Winona is a wolf' 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
  0.5::factA.
  0.8::factB.
  0.7::factC.
  %hop1
  0.95::factX:-and(factB,factC).
  0.1::factY:-or(factA,factC).
  0.1::factZ:-or(factC,factA).

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

  query(conclusion).
  
Either 'Winona is a wolf' or 'Greg is gray' but not both.