% From The Art of Eyepl, Chapter 25.
active_badge(Person, Badge) :-
  badge(Badge, Person),
  badge_status(Badge, active).

cleared_for(Badge, Zone) :-
  badge_clearance(Badge, Clearance),
  zone_requires(Zone, Clearance).

prepared_for(Person, Zone) :-
  training_valid(Person, Zone).