There is little chance that Winona is a wolf. It is unlikely that Mary got the football. It is probably not the case that Bernhard is a frog. There is a better than even chance that if 'Bernhard is a frog and Mary got the football' then Sandra dropped the milk. It is highly unlikely that if 'Mary got the football and Winona is a wolf' then Julius is yellow. Chances are slight that if either 'Winona is a wolf' or 'Bernhard is a frog' but not both then Greg is gray.
It is likely that either 'Greg is gray' or 'Winona is a wolf' but not both.
It is improbable that either 'Greg is gray' or 'Winona is a wolf' but not both.
It is likely that either 'Greg is gray' or 'Winona is a wolf' 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.
  0.2::factB.
  0.25::factC.
  %hop1
  0.6::factX:-and(factC,factB).
  0.05::factY:-and(factB,factA).
  0.1::factZ:-xor(factA,factC).

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

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