It is impossible that Julius is a swan. There is a better than even chance that Bernhard is white. There is a very good chance that Mary took the football. It is probably the case that if either 'Mary took the football' or 'Julius is a swan' but not both then Emily is a cat. We doubt that if 'Mary took the football' or 'Julius is a swan' or both then John discarded the milk. It is improbable that if either 'Julius is a swan' or 'Mary took the football' but not both then Lily is a frog.
There is a very good chance that 'Mary took the football' or 'John discarded the milk' or both.
There is a very good chance that 'Mary took the football' or 'John discarded the milk' or both.
Chances are slight that 'Mary took the football' or 'John discarded 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
  0.0::factA.
  0.6::factB.
  0.8::factC.
  %hop1
  0.7::factX:-xor(factC,factA).
  0.2::factY:-or(factC,factA).
  0.1::factZ:-xor(factA,factC).

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

  query(conclusion).
  
'Mary took the football' or 'John discarded the milk' or both.