Chances are slight that Sandra got the football. There is a better than even chance that Lily is a swan. It is probably not the case that Gertrude is a sheep. Chances are about even that if 'Lily is a swan and Gertrude is a sheep' then Bernhard is green. It is impossible that if 'Sandra got the football and Lily is a swan' then Mary left the milk. It is highly unlikely that if 'Gertrude is a sheep' or 'Sandra got the football' or both then Antoine is thirsty.
It is highly unlikely that 'Mary left the milk' or 'Lily is a swan' or both.
There is a better than even chance that 'Mary left the milk' or 'Lily is a swan' or both.
It is highly unlikely that 'Mary left the milk' or 'Lily 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
  0.1::factA.
  0.6::factB.
  0.25::factC.
  %hop1
  0.5::factX:-and(factB,factC).
  0.0::factY:-and(factA,factB).
  0.05::factZ:-or(factC,factA).

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

  query(conclusion).
  
'Mary left the milk' or 'Lily is a swan' or both.