Global Computation using Events

October 1998 - December 2001

Overview

An EPSRC grant GR/M22413, funded by Communications and Distributed Systems (CDS). The motivation and objectives were as follows:

We propose to work on the construction of distributed systems using events to glue together their components; the entire Internet can become a plug-and-play domain. To achieve this we shall:

• Develop a means of specifying event class hierarchies using the object model (schema) definition language ODL;
• Study mechanisms for the federation of event models (schemas) that have compatible superclasses;
• Design gateway services to extend the publish, register, notify event paradigm across multiple domains;
• Integrate a role-based access control mechanism (OASIS) with event registration;
• Implement and test above the dominant middleware platforms;
• Support rule-based, declarative authoring of applications.

Our fundamental assumptions are that a realistic global computation paradigm must incorporate heterogeneity, object orientation and persistence. The ODMGs object definition language (ODL) is a superset of OMG's interface definition language (IDL). IDL achieves interworking between distributed components written in disparate programming languages. ODL unifies this with stored data.

Within this framework we shall show how to compose distributed applications using events, through our publish, register, notify event paradigm. We will develop an event classification hierarchy so that registration of interest with a superclass can be extended to new subclasses within a domain and to unknown subclasses in other domains; thus achieving schema evolution and federation of event systems.

We shall design and implement event brokerage gateway services. They will discover services which notify events, register and deregister interest as appropriate, assist in event filtering and transport, extend access control as specified by policy. Implementation will be as a layer above dominant platforms such as CORBA, ActiveX and JavaBeans.

We shall support authoring of applications in a rule-based (event-condition-action) declarative language, which includes composite events.

The following people are involved in the project:

• Jean Bacon
• Ken Moody
• John Bates
• Chaoying Ma
• Alexis Hombrecher
• Oliver Seidel

Reports

Here is the six-page report to EPSRC on the outcomes of the grant and here is an appendix, listing related publications.