It is unlikely that Jeff dropped the apple. There is little chance that Fred went to the garden. It is unlikely that Julius is white. We believe that if either 'Julius is white' or 'Fred went to the garden' but not both then Jessica is a cat. It is probably the case that if 'Julius is white and Jeff dropped the apple' then John left the apple. It is improbable that if 'Fred went to the garden and Jeff dropped the apple' then Winona is a mouse.
It is probable that 'Jeff dropped the apple' or 'Fred went to the garden' or both.
It is probably not the case that 'Jeff dropped the apple' or 'Fred went to the garden' or both.
It is probable that 'Jeff dropped the apple' or 'Fred went to the garden' 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
  0.2::factA.
  0.1::factB.
  0.2::factC.
  %hop1
  0.75::factX:-xor(factC,factB).
  0.7::factY:-and(factC,factA).
  0.1::factZ:-and(factB,factA).

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

  query(conclusion).
  
'Jeff dropped the apple' or 'Fred went to the garden' or both.