context: Chances are about even that Gertrude is a cat. It is certain that Sandra dropped the milk. We doubt that Greg is a rhino.
hypothesis: We doubt that 'Greg is a rhino and Sandra dropped the milk'.
valid_hypothesis: We doubt that 'Greg is a rhino and Sandra dropped the milk'.
invalid_hypothesis: It is probable that 'Greg is a rhino and Sandra dropped the milk'.
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
    0.5::factA.
    1.0::factB.
    0.2::factC.
    
  
    %hop2
    conclusion:-and(factC,factB).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is a rhino and Sandra dropped the milk'.