It is probably not the case that Brian is a rhino. Chances are about even that Julius is a swan. It is probably not the case that Bernhard is yellow. It is probably not the case that if either 'Brian is a rhino' or 'Julius is a swan' but not both then Greg is gray. It is highly likely that if 'Julius is a swan' or 'Bernhard is yellow' or both then John took the football. It is probably not the case that if either 'Brian is a rhino' or 'Bernhard is yellow' but not both then Winona is a wolf.
Chances are about even that either 'Julius is a swan' or 'Greg is gray' but not both.
Chances are about even that either 'Julius is a swan' or 'Greg is gray' but not both.
It is impossible that either 'Julius is a swan' or 'Greg 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
  0.25::factA.
  0.5::factB.
  0.25::factC.
  %hop1
  0.25::factX:-xor(factA,factB).
  0.9::factY:-or(factB,factC).
  0.25::factZ:-xor(factA,factC).

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

  query(conclusion).
  
Either 'Julius is a swan' or 'Greg is gray' but not both.