There is a very good chance that Julius is a frog. It is highly unlikely that Brian is a swan. Chances are slight that Lily is green. It is probably not the case that if 'Julius is a frog' or 'Lily is green' or both then Daniel left the apple. There is a very good chance that if either 'Lily is green' or 'Brian is a swan' but not both then John took the milk. We doubt that if 'Julius is a frog and Brian is a swan' then Mary went to the bedroom.
There is a very good chance that either 'Julius is a frog' or 'Mary went to the bedroom' but not both.
There is a very good chance that either 'Julius is a frog' or 'Mary went to the bedroom' but not both.
It is unlikely that either 'Julius is a frog' or 'Mary went to the bedroom' 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
  0.8::factA.
  0.05::factB.
  0.1::factC.
  %hop1
  0.25::factX:-or(factA,factC).
  0.8::factY:-xor(factC,factB).
  0.2::factZ:-and(factA,factB).

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

  query(conclusion).
  
Either 'Julius is a frog' or 'Mary went to the bedroom' but not both.