The Å Publish/Subscribe Framework

This paper describes the design and implementation of a novel decentralized publish/subscribe framework. The primary goal of the design was for a high level of end-developer and user accessibility and simplicity. Furthermore, it was desired to have strong support for occasionally-connected clients and support for mobile and web-based systems. Content-based event patterns can be defined using scripts, with many common script languages supported. Script-based, stateful event patterns permit rich expressiveness, simplify client development and reduce network usage. The framework also offers event persistence, caching and publisher quenching. We also describe a number of applications already built on the framework, for example publishers to support location and presence awareness and ambient visualizations of financial data.