There is little chance that Lily is a swan. It is likely that Julius is green. It is impossible that Gertrude is a sheep. Chances are about even that if 'Lily is a swan and Julius is green' then Mary went to the office. It is certain that if 'Gertrude is a sheep and Julius is green' then Brian is gray. There is almost no chance that if either 'Lily is a swan' or 'Gertrude is a sheep' but not both then Sandra dropped the milk.
There is a very good chance that 'Lily is a swan' or 'Sandra dropped the milk' or both.
It is improbable that 'Lily is a swan' or 'Sandra dropped the milk' or both.
There is a very good chance that 'Lily is a swan' or 'Sandra dropped 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
  0.1::factA.
  0.7::factB.
  0.0::factC.
  %hop1
  0.5::factX:-and(factA,factB).
  1.0::factY:-and(factC,factB).
  0.02::factZ:-xor(factA,factC).

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

  query(conclusion).
  
'Lily is a swan' or 'Sandra dropped the milk' or both.