context: There is a very good chance that Brian is white. We believe that Bernhard is a swan. It is improbable that Greg is a frog.
hypothesis: We believe that 'Bernhard is a swan' or 'Greg is a frog' or both.
valid_hypothesis: We believe that 'Bernhard is a swan' or 'Greg is a frog' or both.
invalid_hypothesis: It is probably not the case that 'Bernhard is a swan' or 'Greg is a frog' or 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
    0.8::factA.
    0.75::factB.
    0.1::factC.
    
  
    %hop2
    conclusion:-or(factB,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'Bernhard is a swan' or 'Greg is a frog' or both.