Chances are slight that Julius is white. It is certain that Mary dropped the milk. It is highly likely that Lily is gray. It is unlikely that if 'Mary dropped the milk' or 'Lily is gray' or both then Jason is tired. It is unlikely that if 'Mary dropped the milk' or 'Lily is gray' or both then Yann is thirsty. It is impossible that if 'Julius is white' or 'Mary dropped the milk' or both then Bill moved to the office.
There is a better than even chance that 'Yann is thirsty and Jason is tired'.
It is highly unlikely that 'Yann is thirsty and Jason is tired'.
There is a better than even chance that 'Yann is thirsty and Jason is tired'.

  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.
  1.0::factB.
  0.9::factC.
  %hop1
  0.2::factX:-or(factB,factC).
  0.2::factY:-or(factB,factC).
  0.0::factZ:-or(factA,factB).

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

  query(conclusion).
  
'Yann is thirsty and Jason is tired'.