context: It is certain that Greg is a swan. There is almost no chance that Julius is a rhino. There is a very good chance that Jeff went to the hallway.
hypothesis: We doubt that 'Greg is a swan and Jeff went to the hallway'.
valid_hypothesis: There is a very good chance that 'Greg is a swan and Jeff went to the hallway'.
invalid_hypothesis: We doubt that 'Greg is a swan and Jeff went to the hallway'.
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
    1.0::factA.
    0.02::factB.
    0.8::factC.
    
  
    %hop2
    conclusion:-and(factA,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is a swan and Jeff went to the hallway'.