Chances are about even that Brian is white. It is certain that Mary discarded the milk. It is almost certain that Julius is a frog. It is improbable that if 'Julius is a frog and Brian is white' then Bernhard is a lion. There is almost no chance that if 'Julius is a frog and Brian is white' then Sandra left the milk. It is certain that if 'Julius is a frog and Brian is white' then Greg is white.
It is almost certain that either 'Brian is white' or 'Bernhard is a lion' but not both.
Chances are about even that either 'Brian is white' or 'Bernhard is a lion' but not both.
It is almost certain that either 'Brian is white' or 'Bernhard is a lion' 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.
  1.0::factB.
  0.95::factC.
  %hop1
  0.1::factX:-and(factC,factA).
  0.02::factY:-and(factC,factA).
  1.0::factZ:-and(factC,factA).

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

  query(conclusion).
  
Either 'Brian is white' or 'Bernhard is a lion' but not both.