context: We doubt that Bernhard is a swan. It is unlikely that Sandra dropped the milk. There is almost no chance that Brian is a swan.
hypothesis: There is a better than even chance that 'Bernhard is a swan and Brian is a swan'.
valid_hypothesis: It is impossible that 'Bernhard is a swan and Brian is a swan'.
invalid_hypothesis: There is a better than even chance that 'Bernhard is a swan and Brian is a swan'.
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.
    0.2::factB.
    0.02::factC.
    
  
    %hop2
    conclusion:-and(factA,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'Bernhard is a swan and Brian is a swan'.