It is almost certain that Yann is tired. There is a very good chance that Julius is gray. There is almost no chance that Winona is a wolf. It is certain that if 'Julius is gray and Yann is tired' then Jeff dropped the apple. It is probable that if 'Yann is tired' or 'Julius is gray' or both then Mary left the football. It is impossible that if either 'Yann is tired' or 'Winona is a wolf' but not both then Lily is a swan.
We believe that 'Jeff dropped the apple and Yann is tired'.
We believe that 'Jeff dropped the apple and Yann is tired'.
Chances are slight that 'Jeff dropped the apple and Yann 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
  0.95::factA.
  0.8::factB.
  0.02::factC.
  %hop1
  1.0::factX:-and(factB,factA).
  0.7::factY:-or(factA,factB).
  0.0::factZ:-xor(factA,factC).

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

  query(conclusion).
  
'Jeff dropped the apple and Yann is tired'.