We doubt that Julius is white. It is probably not the case that Bernhard is a frog. It is probably the case that Jeff left the apple. It is probably not the case that if 'Julius is white' or 'Bernhard is a frog' or both then Yann is bored. It is certain that if 'Julius is white' or 'Jeff left the apple' or both then Sandra got the football. Chances are about even that if 'Jeff left the apple and Julius is white' then John went to the garden.
It is probably not the case that 'Yann is bored' or 'Jeff left the apple' or both.
We believe that 'Yann is bored' or 'Jeff left the apple' or both.
It is probably not the case that 'Yann is bored' or 'Jeff 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
  0.2::factA.
  0.25::factB.
  0.7::factC.
  %hop1
  0.25::factX:-or(factA,factB).
  1.0::factY:-or(factA,factC).
  0.5::factZ:-and(factC,factA).

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

  query(conclusion).
  
'Yann is bored' or 'Jeff left the apple' or both.