Chances are slight that Bernhard is green. It is highly unlikely that Julius is a swan. We doubt that Bill left the milk. Chances are about even that if either 'Bernhard is green' or 'Julius is a swan' but not both then Daniel got the football. There is little chance that if either 'Julius is a swan' or 'Bernhard is green' but not both then Jessica is a mouse. It is almost certain that if either 'Bill left the milk' or 'Bernhard is green' but not both then Mary picked up the apple.
Chances are slight that 'Julius is a swan' or 'Bernhard is green' or both.
Chances are slight that 'Julius is a swan' or 'Bernhard is green' or both.
There is a better than even chance that 'Julius is a swan' or 'Bernhard is green' 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
  0.1::factA.
  0.05::factB.
  0.2::factC.
  %hop1
  0.5::factX:-xor(factA,factB).
  0.1::factY:-xor(factB,factA).
  0.95::factZ:-xor(factC,factA).

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

  query(conclusion).
  
'Julius is a swan' or 'Bernhard is green' or both.