Chances are slight that John discarded the apple. Chances are about even that Lily is a frog. Chances are about even that Julius is gray. It is improbable that if either 'John discarded the apple' or 'Julius is gray' but not both then Emily is a sheep. It is probable that if either 'John discarded the apple' or 'Lily is a frog' but not both then Sandra left the milk. It is likely that if 'Lily is a frog' or 'John discarded the apple' or both then Jessica is a cat.
It is impossible that 'Lily is a frog' or 'Jessica is a cat' or both.
Chances are about even that 'Lily is a frog' or 'Jessica is a cat' or both.
It is impossible that 'Lily is a frog' 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
  0.1::factA.
  0.5::factB.
  0.5::factC.
  %hop1
  0.1::factX:-xor(factA,factC).
  0.7::factY:-xor(factA,factB).
  0.7::factZ:-or(factB,factA).

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

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