This specification describes a CORBA-based Notification Service, a service which<br>extends the existing OMG Event Service, adding to it the following new capabilities:<br>• The ability to transmit events in the form of a well-defined data structure, in<br>addition to Anys and Typed-events as supported by the existing Event Service.<br>• The ability for clients to specify exactly which events they are interested in<br>receiving, by attaching filters to each proxy in a channel.<br>• The ability for the event types required by all consumers of a channel to be<br>discovered by suppliers of that channel, so that suppliers can produce events on<br>demand, or avoid transmitting events in which no consumers have interest.<br>• The ability for the event types offered by suppliers to an event channel to be<br>discovered by consumers of that channel so that consumers may subscribe to new<br>event types as they become available.<br>• The ability to configure various quality of service properties on a per-channel, perproxy,<br>or per-event basis.<br>• An optional event type repository which, if present, facilitates the formation of filter<br>constraints by end-users, by making information about the structure of events which<br>will flow through the channel readily available.<br><br><br>The Notification Service defined here attempts to preserve all of the semantics<br>specified for the OMG Event Service, allowing for interoperability between basic<br>Event Service clients and Notification Service clients. To recap, the OMG Event<br>Service supports asynchronous exchange of event messages between clients. The Event<br>Service introduces event channels which broker event messages, event suppliers which<br>supply event messages, and event consumers which consume event messages.
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