We doubt that Brian is a frog. There is little chance that Julius is white. We doubt that Bill left the milk. There is almost no chance that if 'Bill left the milk and Julius is white' then Mary took the football. It is improbable that if 'Brian is a frog' or 'Bill left the milk' or both then Bernhard is a lion. There is a better than even chance that if either 'Bill left the milk' or 'Brian is a frog' but not both then John went to the kitchen.
It is probably not the case that 'John went to the kitchen' or 'Bill left the milk' or both.
It is probably not the case that 'John went to the kitchen' or 'Bill left the milk' or both.
There is a very good chance that 'John went to the kitchen' or 'Bill left the milk' 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
  0.02::factX:-and(factC,factB).
  0.1::factY:-or(factA,factC).
  0.6::factZ:-xor(factC,factA).

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

  query(conclusion).
  
'John went to the kitchen' or 'Bill left the milk' or both.