Document subclass registers itself against parent class
...to enable automatic selection of the most appropriate class for given record. Naïve API proposal:
item = Event.object(db, pk, pick_best_subclass=True)
This fetches the record and wraps it either in an Event instance or in a more suitable subclass of Event, e.g. "Meeting", "Report", etc.
Use case: a timeline with various records from the same query; each is displayed using the most appropriate template(?). A simple helper can be used to manage templates vs. classes; it is only non-trivial to pick the classes.