It is highly likely that Mary went to the hallway. It is highly likely that Jessica is a sheep. It is probably not the case that Lily is yellow. Chances are about even that if either 'Mary went to the hallway' or 'Jessica is a sheep' but not both then Daniel dropped the milk. We doubt that if 'Jessica is a sheep' or 'Mary went to the hallway' or both then Julius is a rhino. It is almost certain that if either 'Lily is yellow' or 'Mary went to the hallway' but not both then Brian is a swan.
We believe that either 'Julius is a rhino' or 'Mary went to the hallway' but not both.
We believe that either 'Julius is a rhino' or 'Mary went to the hallway' but not both.
It is probably not the case that either 'Julius is a rhino' or 'Mary went to the hallway' 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.
  0.9::factB.
  0.25::factC.
  %hop1
  0.5::factX:-xor(factA,factB).
  0.2::factY:-or(factB,factA).
  0.95::factZ:-xor(factC,factA).

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

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