It is highly likely that Lily is white. There is almost no chance that Fred discarded the apple. Chances are slight that Julius is a frog. It is probable that if 'Lily is white and Julius is a frog' then Greg is a swan. We doubt that if 'Fred discarded the apple' or 'Julius is a frog' or both then John got the milk. It is certain that if either 'Julius is a frog' or 'Lily is white' but not both then Mary went to the bedroom.
It is improbable that 'John got the milk' or 'Lily is white' or both.
It is highly likely that 'John got the milk' or 'Lily is white' or both.
It is improbable that 'John got the milk' or 'Lily is white' or 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
  0.9::factA.
  0.02::factB.
  0.1::factC.
  %hop1
  0.7::factX:-and(factA,factC).
  0.2::factY:-or(factB,factC).
  1.0::factZ:-xor(factC,factA).

  %hop2
  conclusion:-or(factY,factA).

  query(conclusion).
  
'John got the milk' or 'Lily is white' or both.