It is unlikely that Bernhard is green. It is probably the case that Sandra left the milk. It is probably not the case that Greg is a frog. It is probably the case that if 'Sandra left the milk' or 'Bernhard is green' or both then Brian is a swan. It is probable that if either 'Sandra left the milk' or 'Bernhard is green' but not both then Winona is a cat. It is certain that if 'Bernhard is green and Greg is a frog' then John moved to the garden.
It is probably not the case that either 'Bernhard is green' or 'Greg is a frog' but not both.
It is probably not the case that either 'Bernhard is green' or 'Greg is a frog' but not both.
It is likely that either 'Bernhard is green' or 'Greg 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
  0.2::factA.
  0.7::factB.
  0.25::factC.
  %hop1
  0.7::factX:-or(factB,factA).
  0.7::factY:-xor(factB,factA).
  1.0::factZ:-and(factA,factC).

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

  query(conclusion).
  
Either 'Bernhard is green' or 'Greg is a frog' but not both.