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Abstract. Middleware has emerged as an important architectural component in modern distributed systems. Most recently, industry has witnessed the emergence of component-based middleware platforms, such as Enterprise JavaBeans and the CORBA Component Model, aimed at supporting third party development, configuration and subsequent deployment of software. The goal of our research is to extend this work in order to exploit the benefits of componentbased approaches within the middleware platform as well as on top of the platform, the result being more configurable and reconfigurable middleware technologies. This is achieved through a marriage of components with reflection, the latter providing the necessary levels of openness to access the underlying component infrastructure. More specifically, the paper describes in detail the OpenCOM component model, a lightweight and efficient component model based on COM. The paper also describes how OpenCOM can be used to construct a full middleware platform, and also investigates the performance of both OpenCOM and this resultant platform. The main overall contribution of the paper is to demonstrate that flexible middleware technologies can be developed without an adverse effect on the performance of resultant systems.

Abstract. Mobile client applications must discover and interoperate with application services available to them at their present location. However, these services will be developed upon a range of middleware types (e.g. RMI and publish-subscribe) and advertised using different service discovery protocols (e.g. UPnP and SLP) unknown to the application developer. Therefore, a middleware platform supporting mobile client applications should ideally adapt its behaviour to interoperate with any type of discovered service. Furthermore, these applications should be developed independently from particular middleware implementations, as the interaction type is unknown until run-time. This paper presents ReMMoC, a reflective middleware platform that dynamically adapts both its binding and discovery protocol to allow interoperation with heterogeneous services. Furthermore, we present the ReMMoC programming model, which is based upon the Web Services concept of abstract services. We evaluate this work in terms of supporting mobile application development and the memory footprint cost of utilising reflection to create a mobile middleware platform.

A 'second generation' approach to the provision of Grid middleware is now emerging which is built on service-oriented architecture and web services standards and technologies. However, advanced Grid applications have significant demands that are not addressed by present-day web services platforms. As one prime example, current platforms do not support the rich diversity of communication 'interaction types' that are demanded by advanced applications (e.g. publish-subscribe, media streaming, peer-to-peer interaction). In the paper we describe the Gridkit middleware which augments the basic service-oriented architecture to address this particular deficiency. We particularly focus on the communications infrastructure support required to support multiple interaction types in a unified, principled and extensible manner-which we present in terms of the novel concept of pluggable overlay networks.