It is highly likely that Brian is white. It is probable that Winona is a sheep. It is probably the case that Julius is a swan. It is highly unlikely that if either 'Winona is a sheep' or 'Julius is a swan' but not both then Fred left the football. There is a better than even chance that if 'Winona is a sheep' or 'Brian is white' or both then John went to the hallway. It is highly likely that if either 'Brian is white' or 'Julius is a swan' but not both then Greg is a swan.
Chances are about even that either 'John went to the hallway' or 'Julius is a swan' but not both.
Chances are about even that either 'John went to the hallway' or 'Julius is a swan' but not both.
There is almost no chance that either 'John went to the hallway' or 'Julius is a swan' 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
  0.9::factA.
  0.7::factB.
  0.7::factC.
  %hop1
  0.05::factX:-xor(factB,factC).
  0.6::factY:-or(factB,factA).
  0.9::factZ:-xor(factA,factC).

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

  query(conclusion).
  
Either 'John went to the hallway' or 'Julius is a swan' but not both.