Chances are about even that Julius is a swan. There is a better than even chance that Greg is a lion. It is improbable that Bernhard is white. It is impossible that if 'Julius is a swan' or 'Greg is a lion' or both then Lily is a lion. It is improbable that if either 'Greg is a lion' or 'Julius is a swan' but not both then Mary went to the office. It is highly likely that if 'Julius is a swan' or 'Greg is a lion' or both then Brian is a rhino.
We doubt that either 'Mary went to the office' or 'Brian is a rhino' but not both.
It is probable that either 'Mary went to the office' or 'Brian is a rhino' but not both.
We doubt that either 'Mary went to the office' or 'Brian is a rhino' 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.
  0.6::factB.
  0.1::factC.
  %hop1
  0.0::factX:-or(factA,factB).
  0.1::factY:-xor(factB,factA).
  0.9::factZ:-or(factA,factB).

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

  query(conclusion).
  
Either 'Mary went to the office' or 'Brian is a rhino' but not both.