It is probably not the case that Jeff went to the garden. It is probably the case that Gertrude is a cat. There is little chance that Lily is yellow. It is highly unlikely that if either 'Lily is yellow' or 'Gertrude is a cat' but not both then Julius is white. It is highly unlikely that if 'Gertrude is a cat and Lily is yellow' then Fred dropped the milk. It is probably the case that if either 'Lily is yellow' or 'Gertrude is a cat' but not both then Brian is yellow.
It is probably not the case that either 'Julius is white' or 'Jeff went to the garden' but not both.
It is probably not the case that either 'Julius is white' or 'Jeff went to the garden' but not both.
It is almost certain that either 'Julius is white' or 'Jeff went to the garden' 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
  0.25::factA.
  0.7::factB.
  0.1::factC.
  %hop1
  0.05::factX:-xor(factC,factB).
  0.05::factY:-and(factB,factC).
  0.7::factZ:-xor(factC,factB).

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

  query(conclusion).
  
Either 'Julius is white' or 'Jeff went to the garden' but not both.