It is highly unlikely that John picked up the apple. We believe that Brian is a lion. Chances are about even that Emily is a mouse. We doubt that if either 'Brian is a lion' or 'Emily is a mouse' but not both then Julius is a swan. It is impossible that if 'John picked up the apple' or 'Emily is a mouse' or both then Daniel got the football. It is likely that if 'John picked up the apple and Emily is a mouse' then Bernhard is a rhino.
Chances are about even that either 'Emily is a mouse' or 'John picked up the apple' but not both.
Chances are about even that either 'Emily is a mouse' or 'John picked up the apple' but not both.
It is impossible that either 'Emily is a mouse' or 'John picked up the apple' 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
  0.05::factA.
  0.75::factB.
  0.5::factC.
  %hop1
  0.2::factX:-xor(factB,factC).
  0.0::factY:-or(factA,factC).
  0.7::factZ:-and(factA,factC).

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

  query(conclusion).
  
Either 'Emily is a mouse' or 'John picked up the apple' but not both.