context: There is almost no chance that Sandra dropped the milk. It is certain that John went to the hallway. We believe that Greg is a frog.
hypothesis: We believe that 'John went to the hallway and Greg is a frog'.
valid_hypothesis: We believe that 'John went to the hallway and Greg is a frog'.
invalid_hypothesis: It is improbable that 'John went to the hallway and Greg is a frog'.
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
    0.02::factA.
    1.0::factB.
    0.75::factC.
    
  
    %hop2
    conclusion:-and(factB,factC).
  
    query(conclusion).
    
hypothesis_assertion: 'John went to the hallway and Greg is a frog'.