Middleware for Distributed Systems Evolving the Common Structure for Network-centric Applications

Two fundamental trends influence the way we conceive and construct new computing and information systems. The first is that information technology of all forms is becoming highly commoditized i.e., hardware and software artifacts are getting faster, cheaper, and better at a relatively predictable rate. The second is the growing acceptance of a network-centric paradigm, where distributed applications with a range of quality of service (QoS) needs are constructed by integrating separate components connected by various forms of communication services. The nature of this interconnection can range from 1. The very small and tightly coupled, such as avionics mission computing systems to 2. The very large and loosely coupled, such as global telecommunications systems. The interplay of these two trends has yielded new architectural concepts and services embodying layers of middleware. These layers are interposed between applications and commonly available hardware and software infrastructure to make it feasible, easier, and more cost effective to develop and evolve systems using reusable software. Middleware stems from recognizing the need for more advanced and capable support–beyond simple connectivity–to construct effective distributed systems. A significant portion of middleware-oriented R&D activities over the past decade have focused on 1. The identification, evolution, and expansion of our understanding of current middleware services in providing this style of development and