It is improbable that Brian is a rhino. It is impossible that Lily is a swan. Chances are slight that John left the football. There is almost no chance that if 'John left the football and Brian is a rhino' then Jessica is a cat. It is improbable that if 'Lily is a swan' or 'John left the football' or both then Julius is a frog. There is little chance that if either 'John left the football' or 'Lily is a swan' but not both then Emily is a wolf.
It is certain that either 'Brian is a rhino' or 'John left the football' but not both.
We doubt that either 'Brian is a rhino' or 'John left the football' but not both.
It is certain that either 'Brian is a rhino' or 'John left the football' 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
  0.1::factA.
  0.0::factB.
  0.1::factC.
  %hop1
  0.02::factX:-and(factC,factA).
  0.1::factY:-or(factB,factC).
  0.1::factZ:-xor(factC,factB).

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

  query(conclusion).
  
Either 'Brian is a rhino' or 'John left the football' but not both.