Key actors in notification

Senders are instances that notify other instances of changes to themselves; exactly which changes are up to the sender. The sender defines the interest and the notification corresponding to each change. Senders usually inherit from one of the notifier mixins to provide the notifier protocol. Sender instances can perform the notification themselves, or they can share a notifier with other instances.

Receivers register interest in and respond to notifications from senders. Often, they are instances of derived classes of MCollectible, although they can be global or static member functions. Receivers get notifications through a connection. Generally, each receiver owns a connection instance. Connections manage the link to the sender, while receivers implement the responses to the notifications.

Interests identify a sender and an event. A sender provides protocol for creating particular interests in events about which it notifies. A receiver uses this protocol to identify the events about which the sender should notify it.

A notification conveys news of an event to receivers. When a sender undergoes a change for which it has declared it will provide notification, it uses the appropriate interest, and possibly additional notification-specific data, to create a notification. Then, the sender calls Notify to send the notification along to the receivers that want it.