It is highly unlikely that John got the milk. It is highly unlikely that Winona is a cat. It is likely that Brian is yellow. It is probably the case that if 'John got the milk' or 'Brian is yellow' or both then Lily is a swan. Chances are about even that if 'Winona is a cat' or 'Brian is yellow' or both then Mary went to the kitchen. Chances are slight that if either 'John got the milk' or 'Winona is a cat' but not both then Julius is a frog.
It is unlikely that 'Lily is a swan' or 'Brian is yellow' or both.
It is probably the case that 'Lily is a swan' or 'Brian is yellow' or both.
It is unlikely that 'Lily is a swan' or 'Brian is yellow' 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
  0.05::factA.
  0.05::factB.
  0.7::factC.
  %hop1
  0.7::factX:-or(factA,factC).
  0.5::factY:-or(factB,factC).
  0.1::factZ:-xor(factA,factB).

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

  query(conclusion).
  
'Lily is a swan' or 'Brian is yellow' or both.