This is the notification of events from one or more repository. A user registers for notification of a change in a specific piece of content, a content container, or a qualification of a piece of content. The principal actor is the user who is interested in the changed content and the system that registers the event and notifies the user.
Most systems can probably handle individual update requests. Updates to containers such as folders are also probably supported. Creation of objects can potentially be registered by type or location. Direct location can probably be supported much more easily than recursively. Observation by general query and arbitrary predicate can be very difficult to implement and requires a specialized reverse query mechanism.
User ï¿½ user interested in a specific content item
Content System ï¿½ content repository as a notification can only be placed on a specific repository (or should it ï¿½ can this be aggregated? Can this be an Enterprise Service Bus function?)
Messaging System ï¿½ Email, Message Queue, or Instant Messaging system used to deliver notification