context: It is impossible that Sandra grabbed the milk. It is highly unlikely that Brian is yellow. There is a very good chance that Gertrude is a sheep.
hypothesis: We believe that either 'Brian is yellow' or 'Gertrude is a sheep' but not both.
valid_hypothesis: We believe that either 'Brian is yellow' or 'Gertrude is a sheep' but not both.
invalid_hypothesis: We doubt that either 'Brian is yellow' or 'Gertrude is a sheep' 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
    0.0::factA.
    0.05::factB.
    0.8::factC.
    
  
    %hop2
    conclusion:-xor(factB,factC).
  
    query(conclusion).
    
hypothesis_assertion: Either 'Brian is yellow' or 'Gertrude is a sheep' but not both.