context: Chances are about even that Greg is a swan. We doubt that Sumit is tired. It is unlikely that Sandra left the apple.
hypothesis: Chances are slight that 'Greg is a swan and Sandra left the apple'.
valid_hypothesis: Chances are slight that 'Greg is a swan and Sandra left the apple'.
invalid_hypothesis: There is a very good chance that 'Greg is a swan and Sandra left the apple'.
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.
    0.2::factB.
    0.2::factC.
    
  
    %hop2
    conclusion:-and(factA,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'Greg is a swan and Sandra left the apple'.