Using events for the scalable federation of heterogeneous components

Abstract

The thesis of this paper is that, using our eventbased development principles, components that were not designed to interoperate, can be made to work together quickly and easily. The only requirement is that each component must be made event-based by adding an interface for registering interest in events and an interface for injecting actions. A component notifies an event to a distributed client if the parameters of an event, internal to the component, match the parameters of a particular registration. Heterogeneous components can be federated using event-based rules; rules can respond to events from any component by injecting actions into any other component. We show that the event paradigm is scaiable by illustrating how event-based components can be located worldwide, using a federation of event brokers. Additionally, we illustrate with 3 event-based systems we have developed: a component-based multimedia system, a multi-user virtual worlds system and an augmented reality system for mobile users. Finally, we show how the event paradigm is also scalable enough to allow event federation of entire systems, not just single components. We illustrate by showing how we have federated the operation of the 3 featured eventbased systems. This enables, for example, real-world mobile users to appear as avatars in the appropriate locations in the VR world, and for these avatars to move in response to actual user movements.

Context Awareness: An Experiment with Hoarding

“…This must be implemented with some kind of distributed event processing. There are several approaches to this issue [7][8][9][10]. Bates [7] defends a framework for a federation of heterogeneous components connected, transparently, by distributed events in a publisher-subscriber model.…”

Federating heterogeneous event services

“…In [5] events are used to federate components of any granularity including event services. Similar to the FES, the approach in [6] uses a common event model and gateways to provide interoperability between event services.…”

Supporting Mobility in Content-Based Publish/Subscribe Middleware

“…Subject-and type-based addressing exists [22,2,8], but the most flexible scheme is offered by content-based filtering [19]. Filters are boolean functions on the entire content of a notification and a common way to implement subscriptions.…”