||This interface describes any system event.
||The iEventCord is an interface provided by an event queue to any event
handlers wanting to receive some subclasses of events ASAP in a specified
priority, bypassing the queue itself.
||This interface describes an entity that can receive events.
||The iEventOutlet is the interface to an object that is provided by an event
queue to every event plug when it registers itself.
||Event plug interface, also referred as "event source".