Chances are about even that John put down the apple. It is probably not the case that Bernhard is a frog. It is unlikely that Mary got the football. It is unlikely that if either 'John put down the apple' or 'Mary got the football' but not both then Bill moved to the office. It is improbable that if 'Bernhard is a frog' or 'John put down the apple' or both then Jessica is a cat. It is unlikely that if 'Bernhard is a frog and John put down the apple' then Greg is white.
It is certain that either 'Mary got the football' or 'Bill moved to the office' but not both.
It is probably not the case that either 'Mary got the football' or 'Bill moved to the office' but not both.
It is certain that either 'Mary got the football' or 'Bill moved to the office' 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.
  0.25::factB.
  0.2::factC.
  %hop1
  0.2::factX:-xor(factA,factC).
  0.1::factY:-or(factB,factA).
  0.2::factZ:-and(factB,factA).

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

  query(conclusion).
  
Either 'Mary got the football' or 'Bill moved to the office' but not both.