Chances are slight that Greg is a swan. There is almost no chance that John got the milk. It is highly unlikely that Winona is a mouse. There is a better than even chance that if 'Greg is a swan and John got the milk' then Bill moved to the office. It is probably not the case that if 'John got the milk and Greg is a swan' then Julius is gray. It is highly likely that if 'John got the milk and Winona is a mouse' then Gertrude is a sheep.
It is impossible that 'Winona is a mouse and John got the milk'.
It is impossible that 'Winona is a mouse and John got the milk'.
It is probably the case that 'Winona is a mouse and John got the milk'.

  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.
  0.02::factB.
  0.05::factC.
  %hop1
  0.6::factX:-and(factA,factB).
  0.25::factY:-and(factB,factA).
  0.9::factZ:-and(factB,factC).

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

  query(conclusion).
  
'Winona is a mouse and John got the milk'.