It is certain that Mary left the football. It is highly unlikely that John moved to the office. There is almost no chance that Julius is a lion. It is impossible that if 'Julius is a lion' or 'John moved to the office' or both then Yann is thirsty. It is highly likely that if 'Mary left the football' or 'Julius is a lion' or both then Greg is a swan. It is probably not the case that if 'Julius is a lion' or 'John moved to the office' or both then Daniel put down the milk.
It is impossible that 'Greg is a swan and Yann is thirsty'.
It is impossible that 'Greg is a swan and Yann is thirsty'.
It is certain that 'Greg is a swan and Yann is thirsty'.

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

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

  query(conclusion).
  
'Greg is a swan and Yann is thirsty'.