We doubt that Yann is bored. It is impossible that Bernhard is gray. It is highly likely that John went to the kitchen. It is highly likely that if 'Yann is bored' or 'John went to the kitchen' or both then Brian is white. We believe that if either 'John went to the kitchen' or 'Bernhard is gray' but not both then Sandra left the football. Chances are about even that if 'Yann is bored and Bernhard is gray' then Julius is a frog.
Chances are slight that 'Bernhard is gray' or 'Brian is white' or both.
There is a very good chance that 'Bernhard is gray' or 'Brian is white' or both.
Chances are slight that 'Bernhard is gray' or 'Brian is white' 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.
  0.0::factB.
  0.9::factC.
  %hop1
  0.9::factX:-or(factA,factC).
  0.75::factY:-xor(factC,factB).
  0.5::factZ:-and(factA,factB).

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

  query(conclusion).
  
'Bernhard is gray' or 'Brian is white' or both.