context: We doubt that Lily is white. There is a very good chance that John picked up the apple. Chances are slight that Bernhard is a rhino.
hypothesis: We believe that either 'John picked up the apple' or 'Bernhard is a rhino' but not both.
valid_hypothesis: We believe that either 'John picked up the apple' or 'Bernhard is a rhino' but not both.
invalid_hypothesis: We doubt that either 'John picked up the apple' or 'Bernhard is a rhino' but not both.
problog: 
    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
    0.2::factA.
    0.8::factB.
    0.1::factC.
    
  
    %hop2
    conclusion:-xor(factB,factC).
  
    query(conclusion).
    
hypothesis_assertion: Either 'John picked up the apple' or 'Bernhard is a rhino' but not both.