We believe that John left the apple. There is little chance that Julius is gray. It is impossible that Bernhard is a frog. It is likely that if 'John left the apple and Bernhard is a frog' then Emily is a sheep. There is a better than even chance that if 'Bernhard is a frog' or 'Julius is gray' or both then Antoine is thirsty. Chances are about even that if 'Julius is gray and Bernhard is a frog' then Daniel grabbed the apple.
It is impossible that either 'Daniel grabbed the apple' or 'Bernhard is a frog' but not both.
It is impossible that either 'Daniel grabbed the apple' or 'Bernhard is a frog' but not both.
It is almost certain that either 'Daniel grabbed the apple' or 'Bernhard 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
  0.75::factA.
  0.1::factB.
  0.0::factC.
  %hop1
  0.7::factX:-and(factA,factC).
  0.6::factY:-or(factC,factB).
  0.5::factZ:-and(factB,factC).

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

  query(conclusion).
  
Either 'Daniel grabbed the apple' or 'Bernhard is a frog' but not both.