Chances are slight that John put down the milk. It is probable that Jeff moved to the garden. Chances are about even that Greg is a lion. We believe that if either 'Jeff moved to the garden' or 'Greg is a lion' but not both then Brian is a frog. It is improbable that if either 'Greg is a lion' or 'John put down the milk' but not both then Jessica is a cat. It is certain that if 'John put down the milk and Greg is a lion' then Julius is a swan.
It is impossible that either 'Brian is a frog' or 'Jeff moved to the garden' but not both.
There is a better than even chance that either 'Brian is a frog' or 'Jeff moved to the garden' but not both.
It is impossible that either 'Brian is a frog' or 'Jeff moved to the garden' 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.
  0.7::factB.
  0.5::factC.
  %hop1
  0.75::factX:-xor(factB,factC).
  0.1::factY:-xor(factC,factA).
  1.0::factZ:-and(factA,factC).

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

  query(conclusion).
  
Either 'Brian is a frog' or 'Jeff moved to the garden' but not both.