The relation service is a notification broadcaster that notifies listeners of events affecting relations. It sends RelationNotification objects in the following cases:
A new relation is created: The notification contains its identifier and its relation type
An existing relation is updated: In addition to the relation identifier and type, the notification contains the list of names, the list of new values, and the list of old values for all roles that have been modified
A relation is removed: The notification contains its identifier and its relation type
There are three equivalent notification types for events affecting relations defined as external MBeans (see 13.3 Objects Representing Relations). In addition to the role and relation information, these notifications contain the object name of this MBean.