It is probably not the case that John went to the bedroom. It is unlikely that Gertrude is a sheep. It is probably not the case that Julius is a frog. There is little chance that if 'John went to the bedroom' or 'Gertrude is a sheep' or both then Brian is a rhino. It is highly likely that if either 'John went to the bedroom' or 'Julius is a frog' but not both then Greg is white. Chances are slight that if 'John went to the bedroom and Julius is a frog' then Winona is a cat.
It is probably not the case that either 'John went to the bedroom' or 'Brian is a rhino' but not both.
It is probably not the case that either 'John went to the bedroom' or 'Brian is a rhino' but not both.
It is almost certain that either 'John went to the bedroom' or 'Brian is a rhino' 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.
  0.2::factB.
  0.25::factC.
  %hop1
  0.1::factX:-or(factA,factB).
  0.9::factY:-xor(factA,factC).
  0.1::factZ:-and(factA,factC).

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

  query(conclusion).
  
Either 'John went to the bedroom' or 'Brian is a rhino' but not both.