It is highly likely that Julius is white. It is unlikely that Brian is a swan. We doubt that John went to the bedroom. We believe that if either 'John went to the bedroom' or 'Julius is white' but not both then Bernhard is a rhino. It is certain that if either 'Julius is white' or 'John went to the bedroom' but not both then Gertrude is a mouse. There is a very good chance that if 'John went to the bedroom' or 'Brian is a swan' or both then Mary left the football.
We believe that 'Bernhard is a rhino' or 'Mary left the football' or both.
We believe that 'Bernhard is a rhino' or 'Mary left the football' or both.
Chances are slight that 'Bernhard is a rhino' or 'Mary left the football' 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
  0.9::factA.
  0.2::factB.
  0.2::factC.
  %hop1
  0.75::factX:-xor(factC,factA).
  1.0::factY:-xor(factA,factC).
  0.8::factZ:-or(factC,factB).

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

  query(conclusion).
  
'Bernhard is a rhino' or 'Mary left the football' or both.