% From The Art of EyeProlog, Chapter 25 — Decision, reasons, and proof.
:- use_module(library(lists)).

permit(Person, Zone) :-
  active_badge(Person, Badge),
  cleared_for(Badge, Zone),
  prepared_for(Person, Zone),
  in_good_standing(Person).

reason(Person, Zone, badge_and_training_verified) :-
  permit(Person, Zone).