We focused on the design of an architectural framework for event handling and showed how COBEA can be used to build large-scale distributed active systems under various application scenarios. We also reported our preliminary experience of using COBEA for building real applications.
COBEA supports the fundamental building blocks for developing active event-driven systems, namely the primitives, the mediator and the composite event service. The primitives form the foundation of the COBEA event architecture, in which the publish-register-notify mode is well supported for efficient asynchronous event communication. The mediator decouples the supplier from the consumer by accepting events from the suppliers, and passing events only to the interested consumers. Thus the supplier and the consumer do not have to know each other in order to communicate events. The composite event service, in particular, provides a powerful means of composing events via a number of operators and a convenient interface for the user to specify composite events. The distributed implementation of the service includes an evaluation engine for composite events, events timestamped at source, event streams and fault tolerance in the form of a heartbeat protocol.
The work focuses on the Notification Model and features well-defined interfaces for event registration, notification and filtering. Future work for COBEA includes incorporating security measures and implementing support for reliable event delivery.