Chances are about even that Jeff discarded the milk. There is almost no chance that Daniel left the football. There is a better than even chance that Lily is green. It is probable that if either 'Lily is green' or 'Daniel left the football' but not both then Brian is a rhino. It is unlikely that if either 'Jeff discarded the milk' or 'Daniel left the football' but not both then Julius is yellow. There is a very good chance that if 'Jeff discarded the milk' or 'Daniel left the football' or both then Bernhard is a swan.
Chances are about even that either 'Bernhard is a swan' or 'Daniel left the football' but not both.
Chances are about even that either 'Bernhard is a swan' or 'Daniel left the football' but not both.
It is impossible that either 'Bernhard is a swan' or 'Daniel left the football' 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
  0.5::factA.
  0.02::factB.
  0.6::factC.
  %hop1
  0.7::factX:-xor(factC,factB).
  0.2::factY:-xor(factA,factB).
  0.8::factZ:-or(factA,factB).

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

  query(conclusion).
  
Either 'Bernhard is a swan' or 'Daniel left the football' but not both.