Foundations of Middleware Technologies
Middleware technologies, such as CORBA, Java, EJB, Jini and Web Services, are becoming increasingly popular for building both embedded and enterprise applications. Unfortunately, a lot of the middleware mechanisms and techniques are mostly in the practitioners' domain, and there has been very little research into the fundamental theoretical and design principles underlying the development of middleware. As middleware gains widespread adoption, it becomes essential to investigate, and to capture, the basics and the methodologies of middleware technologies.
There still exist several open issues in middleware that need to be addressed, particularly as the diversity and number of middleware technologies increases with every year. One of the fundamental issues is whether every new middleware platform actually advances the state-of-the-art or the stateof-the-practice in any significant way, or whether it represents yet another buzzword. In order to understand this better, it is necessary to build a body of knowledge (based on our current practical experience with middleware) that reveals the deeper issues and the basic building blocks of such middleware systems.
This objective of the Workshop on the Foundations of Middleware Technologies, held in Irvine, CA in November 2002, was to serve as a forum for researchers and practitioners in middleware to propose new ideas in the area of design, algorithms, protocols, service specifications, architectures, etc., to form a strong theoretical foundation in the principles underlying middleware systems.
Of the papers and discussions at the workshop, there emerged four strong research directions in middleware that formed the basis for this special issue of Concurrency and Computation: Practice and Experience. It is sheer coincidence that each of these papers represents a different continent, namely, Asia, Australia, Europe and North America: this international representation is, in fact, a testament to the widespread adoption of, and continuing research/interest in, middleware. This special issue captures a variety of research directions, ranging from empirical evaluation to systems development, in the context of message-oriented middleware, real-time fault-tolerant CORBA and publish/subscribe middleware.
On the modeling of publish/subscribe communication systems by Baldoni et al. presents a new formal framework for viewing generic publish/subscribe middleware systems, and for analyzing and evaluating the effectiveness, performance and other guarantees of such systems. The formal model is independent of implementation details, and allows for a variety of strategies to be plugged in so that they can be evaluated; the model also incorporates temporal requirements. Distributed filter processes