It is unlikely that Sandra dropped the milk. There is little chance that Julius is a frog. It is impossible that Lily is a rhino. There is almost no chance that if 'Sandra dropped the milk and Julius is a frog' then Brian is green. It is probably not the case that if either 'Sandra dropped the milk' or 'Julius is a frog' but not both then John discarded the apple. It is highly likely that if 'Julius is a frog' or 'Lily is a rhino' or both then Winona is a sheep.
It is improbable that either 'John discarded the apple' or 'Julius is a frog' but not both.
It is improbable that either 'John discarded the apple' or 'Julius is a frog' but not both.
There is a better than even chance that either 'John discarded the apple' or 'Julius is a frog' but not 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
  0.2::factA.
  0.1::factB.
  0.0::factC.
  %hop1
  0.02::factX:-and(factA,factB).
  0.25::factY:-xor(factA,factB).
  0.9::factZ:-or(factB,factC).

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

  query(conclusion).
  
Either 'John discarded the apple' or 'Julius is a frog' but not both.