There is a better than even chance that Greg is green. There is almost no chance that Lily is white. It is impossible that Daniel got the milk. It is probable that if either 'Lily is white' or 'Daniel got the milk' but not both then Mary dropped the apple. Chances are slight that if 'Lily is white and Greg is green' then Brian is a swan. It is impossible that if either 'Daniel got the milk' or 'Greg is green' but not both then John moved to the office.
It is highly unlikely that either 'Greg is green' or 'Daniel got the milk' but not both.
There is a better than even chance that either 'Greg is green' or 'Daniel got the milk' but not both.
It is highly unlikely that either 'Greg is green' or 'Daniel got the milk' 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
  0.6::factA.
  0.02::factB.
  0.0::factC.
  %hop1
  0.7::factX:-xor(factB,factC).
  0.1::factY:-and(factB,factA).
  0.0::factZ:-xor(factC,factA).

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

  query(conclusion).
  
Either 'Greg is green' or 'Daniel got the milk' but not both.