It is probable that Julius is a frog. We doubt that Greg is a swan. It is almost certain that Winona is a wolf. There is a better than even chance that if 'Winona is a wolf and Greg is a swan' then Emily is a mouse. We believe that if 'Winona is a wolf and Julius is a frog' then Sandra dropped the milk. There is almost no chance that if 'Winona is a wolf' or 'Julius is a frog' or both then John picked up the apple.
We believe that either 'Winona is a wolf' or 'Greg is a swan' but not both.
We believe that either 'Winona is a wolf' or 'Greg is a swan' but not both.
There is little chance that either 'Winona is a wolf' or 'Greg is a swan' 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
  0.7::factA.
  0.2::factB.
  0.95::factC.
  %hop1
  0.6::factX:-and(factC,factB).
  0.75::factY:-and(factC,factA).
  0.02::factZ:-or(factC,factA).

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

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