context: It is highly likely that Greg is a frog. We doubt that Mary left the football. It is highly unlikely that John discarded the milk.
hypothesis: We doubt that 'Mary left the football and Greg is a frog'.
valid_hypothesis: We doubt that 'Mary left the football and Greg is a frog'.
invalid_hypothesis: It is certain that 'Mary left the football 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
    0.9::factA.
    0.2::factB.
    0.05::factC.
    
  
    %hop2
    conclusion:-and(factB,factA).
  
    query(conclusion).
    
hypothesis_assertion: 'Mary left the football and Greg is a frog'.