It is highly unlikely that Jessica is a cat. There is a very good chance that Julius is a swan. It is impossible that Bernhard is gray. We believe that if 'Julius is a swan and Bernhard is gray' then Jeff left the apple. It is highly likely that if either 'Julius is a swan' or 'Jessica is a cat' but not both then Winona is a mouse. It is likely that if 'Bernhard is gray' or 'Julius is a swan' or both then John dropped the apple.
We believe that 'Winona is a mouse' or 'John dropped the apple' or both.
We believe that 'Winona is a mouse' or 'John dropped the apple' or both.
Chances are slight that 'Winona is a mouse' or 'John dropped the apple' or both.

  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
  0.05::factA.
  0.8::factB.
  0.0::factC.
  %hop1
  0.75::factX:-and(factB,factC).
  0.9::factY:-xor(factB,factA).
  0.7::factZ:-or(factC,factB).

  %hop2
  conclusion:-or(factY,factZ).

  query(conclusion).
  
'Winona is a mouse' or 'John dropped the apple' or both.