There is little chance that Lily is white. There is little chance that John discarded the milk. It is highly unlikely that Julius is a swan. It is impossible that if either 'John discarded the milk' or 'Julius is a swan' but not both then Greg is a frog. It is impossible that if 'Julius is a swan' or 'John discarded the milk' or both then Mary went to the bedroom. Chances are about even that if either 'John discarded the milk' or 'Julius is a swan' but not both then Bernhard is gray.
It is certain that 'Mary went to the bedroom and Greg is a frog'.
It is impossible that 'Mary went to the bedroom and Greg is a frog'.
It is certain that 'Mary went to the bedroom and Greg 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.
  0.1::factB.
  0.05::factC.
  %hop1
  0.0::factX:-xor(factB,factC).
  0.0::factY:-or(factC,factB).
  0.5::factZ:-xor(factB,factC).

  %hop2
  conclusion:-and(factY,factX).

  query(conclusion).
  
'Mary went to the bedroom and Greg is a frog'.