It is likely that Fred discarded the apple. It is improbable that Julius is white. It is probably not the case that John is in the garden. There is a very good chance that if either 'Julius is white' or 'Fred discarded the apple' but not both then Bernhard is yellow. There is almost no chance that if either 'John is in the garden' or 'Fred discarded the apple' but not both then Brian is a swan. There is almost no chance that if 'Julius is white and Fred discarded the apple' then Greg is green.
It is improbable that either 'Brian is a swan' or 'Julius is white' but not both.
It is improbable that either 'Brian is a swan' or 'Julius is white' but not both.
It is almost certain that either 'Brian is a swan' or 'Julius is white' 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.
  0.1::factB.
  0.25::factC.
  %hop1
  0.8::factX:-xor(factB,factA).
  0.02::factY:-xor(factC,factA).
  0.02::factZ:-and(factB,factA).

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

  query(conclusion).
  
Either 'Brian is a swan' or 'Julius is white' but not both.