It is certain that Greg is a swan. It is certain that Daniel got the football. There is a very good chance that Mary left the football. It is certain that if 'Daniel got the football and Greg is a swan' then Brian is white. It is improbable that if either 'Mary left the football' or 'Daniel got the football' but not both then Lily is a lion. It is almost certain that if 'Daniel got the football' or 'Mary left the football' or both then John went to the bedroom.
Chances are slight that either 'Lily is a lion' or 'Mary left the football' but not both.
There is a very good chance that either 'Lily is a lion' or 'Mary left the football' but not both.
Chances are slight that either 'Lily is a lion' or 'Mary 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
  1.0::factA.
  1.0::factB.
  0.8::factC.
  %hop1
  1.0::factX:-and(factB,factA).
  0.1::factY:-xor(factC,factB).
  0.95::factZ:-or(factB,factC).

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

  query(conclusion).
  
Either 'Lily is a lion' or 'Mary left the football' but not both.