There is almost no chance that John discarded the milk. Chances are slight that Brian is a rhino. It is probably the case that Bernhard is a swan. Chances are about even that if 'Bernhard is a swan and Brian is a rhino' then Julius is a lion. It is probably the case that if 'Bernhard is a swan and John discarded the milk' then Lily is white. Chances are about even that if 'Bernhard is a swan' or 'Brian is a rhino' or both then Mary got the football.
We doubt that 'Mary got the football' or 'Bernhard is a swan' or both.
It is probably the case that 'Mary got the football' or 'Bernhard is a swan' or both.
We doubt that 'Mary got the football' or 'Bernhard is a swan' 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
  0.02::factA.
  0.1::factB.
  0.7::factC.
  %hop1
  0.5::factX:-and(factC,factB).
  0.7::factY:-and(factC,factA).
  0.5::factZ:-or(factC,factB).

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

  query(conclusion).
  
'Mary got the football' or 'Bernhard is a swan' or both.