Chances are about even that Greg is yellow. It is highly likely that Bernhard is a frog. There is almost no chance that Brian is green. There is almost no chance that if 'Bernhard is a frog' or 'Greg is yellow' or both then Lily is a rhino. We doubt that if either 'Bernhard is a frog' or 'Greg is yellow' but not both then Julius is gray. It is probable that if either 'Bernhard is a frog' or 'Brian is green' but not both then Mary went to the bedroom.
It is highly unlikely that either 'Bernhard is a frog' or 'Julius is gray' but not both.
There is a very good chance that either 'Bernhard is a frog' or 'Julius is gray' but not both.
It is highly unlikely that either 'Bernhard is a frog' or 'Julius is gray' 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.
  0.9::factB.
  0.02::factC.
  %hop1
  0.02::factX:-or(factB,factA).
  0.2::factY:-xor(factB,factA).
  0.7::factZ:-xor(factB,factC).

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

  query(conclusion).
  
Either 'Bernhard is a frog' or 'Julius is gray' but not both.