We doubt that Bernhard is a rhino. It is highly unlikely that Mary went to the garden. It is highly likely that Julius is white. It is probable that if 'Bernhard is a rhino' or 'Julius is white' or both then John left the milk. Chances are about even that if 'Mary went to the garden' or 'Bernhard is a rhino' or both then Greg is yellow. It is unlikely that if either 'Mary went to the garden' or 'Julius is white' but not both then Winona is a wolf.
We doubt that 'Bernhard is a rhino' or 'Julius is white' or both.
It is highly likely that 'Bernhard is a rhino' or 'Julius is white' or both.
We doubt that 'Bernhard is a rhino' or 'Julius 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.
  0.05::factB.
  0.9::factC.
  %hop1
  0.7::factX:-or(factA,factC).
  0.5::factY:-or(factB,factA).
  0.2::factZ:-xor(factB,factC).

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

  query(conclusion).
  
'Bernhard is a rhino' or 'Julius is white' or both.