It is probable that Julius is yellow. We believe that Brian is a swan. Chances are about even that John left the apple. There is a better than even chance that if 'John left the apple' or 'Julius is yellow' or both then Mary went to the office. It is highly likely that if 'John left the apple' or 'Brian is a swan' or both then Bernhard is gray. Chances are about even that if either 'Brian is a swan' or 'John left the apple' but not both then Lily is a lion.
There is a better than even chance that either 'Lily is a lion' or 'John left the apple' but not both.
There is a better than even chance that either 'Lily is a lion' or 'John left the apple' but not both.
There is almost no chance that either 'Lily is a lion' or 'John left the apple' 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
  0.7::factA.
  0.75::factB.
  0.5::factC.
  %hop1
  0.6::factX:-or(factC,factA).
  0.9::factY:-or(factC,factB).
  0.5::factZ:-xor(factB,factC).

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

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