Circumventing Negation as Failure Issue with Ontology

star_rating(jeanluis, 4).
star_rating(francesco, 5).
avg_pph(jeanluis, 72).

good_standard(R) :-
    star_rating(R, S),
    S >= 4.

reasonable(R) :-
    avg_pph(R, P),
    P < 50.

tion