Chances are slight that John grabbed the apple. Chances are about even that Lily is a frog. It is probable that Julius is a swan. There is almost no chance that if either 'Julius is a swan' or 'John grabbed the apple' but not both then Bernhard is green. There is almost no chance that if either 'Lily is a frog' or 'John grabbed the apple' but not both then Fred went to the garden. Chances are slight that if 'Lily is a frog and John grabbed the apple' then Greg is gray.
It is highly likely that 'Greg is gray and Lily is a frog'.
It is impossible that 'Greg is gray and Lily is a frog'.
It is highly likely that 'Greg is gray and Lily is a frog'.

  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
  0.1::factA.
  0.5::factB.
  0.7::factC.
  %hop1
  0.02::factX:-xor(factC,factA).
  0.02::factY:-xor(factB,factA).
  0.1::factZ:-and(factB,factA).

  %hop2
  conclusion:-and(factZ,factB).

  query(conclusion).
  
'Greg is gray and Lily is a frog'.