It is impossible that Winona is a mouse. It is likely that Brian is gray. It is improbable that John left the apple. It is unlikely that if 'Winona is a mouse' or 'John left the apple' or both then Julius is white. It is improbable that if either 'Brian is gray' or 'John left the apple' but not both then Mary went to the office. There is almost no chance that if 'John left the apple and Brian is gray' then Bernhard is gray.
We believe that 'Brian is gray' or 'John left the apple' or both.
We believe that 'Brian is gray' or 'John left the apple' or both.
It is unlikely that 'Brian is gray' or 'John left 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
  0.0::factA.
  0.7::factB.
  0.1::factC.
  %hop1
  0.2::factX:-or(factA,factC).
  0.1::factY:-xor(factB,factC).
  0.02::factZ:-and(factC,factB).

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

  query(conclusion).
  
'Brian is gray' or 'John left the apple' or both.