Chances are about even that Mary left the milk. There is little chance that Greg is a rhino. It is highly likely that Lily is a swan. Chances are slight that if 'Lily is a swan' or 'Greg is a rhino' or both then Julius is gray. We believe that if 'Lily is a swan and Mary left the milk' then Bernhard is a frog. It is highly likely that if 'Greg is a rhino and Lily is a swan' then John got the milk.
Chances are slight that 'John got the milk and Greg is a rhino'.
Chances are slight that 'John got the milk and Greg is a rhino'.
It is probable that 'John got the milk and Greg is a rhino'.

  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
  0.5::factA.
  0.1::factB.
  0.9::factC.
  %hop1
  0.1::factX:-or(factC,factB).
  0.75::factY:-and(factC,factA).
  0.9::factZ:-and(factB,factC).

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

  query(conclusion).
  
'John got the milk and Greg is a rhino'.