It is certain that Emily is a sheep. There is a very good chance that Lily is a frog. It is highly unlikely that John got the milk. It is improbable that if 'Emily is a sheep' or 'John got the milk' or both then Mary went to the hallway. Chances are about even that if 'Emily is a sheep and John got the milk' then Julius is a rhino. It is certain that if either 'Lily is a frog' or 'Emily is a sheep' but not both then Brian is white.
We doubt that either 'Brian is white' or 'Julius is a rhino' but not both.
We doubt that either 'Brian is white' or 'Julius is a rhino' but not both.
There is a very good chance that either 'Brian is white' or 'Julius 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
  1.0::factA.
  0.8::factB.
  0.05::factC.
  %hop1
  0.1::factX:-or(factA,factC).
  0.5::factY:-and(factA,factC).
  1.0::factZ:-xor(factB,factA).

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

  query(conclusion).
  
Either 'Brian is white' or 'Julius is a rhino' but not both.