It is impossible that Julius is yellow. It is impossible that Greg is gray. There is almost no chance that Jeff dropped the apple. It is probably not the case that if 'Julius is yellow' or 'Jeff dropped the apple' or both then Daniel took the milk. It is improbable that if 'Greg is gray and Julius is yellow' then Gertrude is a cat. We doubt that if either 'Jeff dropped the apple' or 'Julius is yellow' but not both then Mary went to the bedroom.
It is highly likely that 'Daniel took the milk' or 'Greg is gray' or both.
It is impossible that 'Daniel took the milk' or 'Greg is gray' or both.
It is highly likely that 'Daniel took the milk' or 'Greg is gray' 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
  0.0::factA.
  0.0::factB.
  0.02::factC.
  %hop1
  0.25::factX:-or(factA,factC).
  0.1::factY:-and(factB,factA).
  0.2::factZ:-xor(factC,factA).

  %hop2
  conclusion:-or(factX,factB).

  query(conclusion).
  
'Daniel took the milk' or 'Greg is gray' or both.