As data changes clients such as UI-level applications need to respond to the updates. The Contacts Model calls a Change Notifier class (CContactChangeNotifier) which allows clients to receive notification of changes made to contact items. Change events are sent in the order that they occur.
Change event details are contained in TContactDbObserverEvent and include:
Changes to a contact item, template, group or own card
Recovery from a damaged database
Rollback from a change to the database has completed
Changes to the current database
Changes to Speed Dials
Changes to the sort order of a contact list
Each notification event specifies the UID of the contact changed, and of the client who made the change (to allow clients to ignore their own changes).