It is impossible that Bernhard is a swan. There is almost no chance that Brian is a frog. It is likely that Jeff left the football. There is a better than even chance that if either 'Bernhard is a swan' or 'Brian is a frog' but not both then Julius is a rhino. There is a very good chance that if 'Jeff left the football' or 'Brian is a frog' or both then Greg is a swan. There is almost no chance that if either 'Bernhard is a swan' or 'Jeff left the football' but not both then John went to the garden.
It is impossible that either 'Julius is a rhino' or 'Brian is a frog' but not both.
It is impossible that either 'Julius is a rhino' or 'Brian is a frog' but not both.
It is highly likely that either 'Julius is a rhino' or 'Brian is a frog' 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
  0.0::factA.
  0.02::factB.
  0.7::factC.
  %hop1
  0.6::factX:-xor(factA,factB).
  0.8::factY:-or(factC,factB).
  0.02::factZ:-xor(factA,factC).

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

  query(conclusion).
  
Either 'Julius is a rhino' or 'Brian is a frog' but not both.