There is a better than even chance that Brian is a frog. It is certain that Lily is a swan. There is little chance that Jessica is a cat. There is almost no chance that if either 'Lily is a swan' or 'Brian is a frog' but not both then Gertrude is a cat. It is probably not the case that if 'Lily is a swan and Brian is a frog' then John put down the milk. It is improbable that if 'Brian is a frog and Jessica is a cat' then Bernhard is white.
It is unlikely that 'Lily is a swan' or 'Jessica is a cat' or both.
It is certain that 'Lily is a swan' or 'Jessica is a cat' or both.
It is unlikely that 'Lily is a swan' or 'Jessica is a cat' 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
  0.6::factA.
  1.0::factB.
  0.1::factC.
  %hop1
  0.02::factX:-xor(factB,factA).
  0.25::factY:-and(factB,factA).
  0.1::factZ:-and(factA,factC).

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

  query(conclusion).
  
'Lily is a swan' or 'Jessica is a cat' or both.