Abstract. Dynamic Aspect Oriented Programming (AOP) technologies typically provide coarse-grained mechanisms for adapting aspects that cross-cut a system deployment; i.e. whole aspect modules can be added and removed at runtime. However, in this paper we demonstrate that adaptation of the finer-grained elements of individual aspect modules is required in highly dynamic systems and applications. We present AspectOpenCOM, a principled, reflection-based component framework that provides a meta object protocol capable of fine-grained adaptation of deployed aspects. We then evaluate this solution by eliciting a set of requirements for dynamic fine-grained adaptation from a series of case studies, and illustrate how the framework successfully meets these criteria. We also investigate the performance gains of fine-grained adaptation versus a coarse-grained approach. 1

The emergence of applications domains such as pervasive and autonomic computing has increased the need for customisation and dynamic adaptation of both distributed systems, and the underlying middleware platforms. Two highly complementary technologies have been advocated to meet these challenges, namely: aspect oriented programming (AOP) and reflective middleware. However, these have so far been considered in isolation, or typically target a particular middleware challenge e.g. using aspects to customise a middleware implementation; or using reflection (or dynamic AOP) to alter runtime behaviour. We believe that in combination these technologies better support the engineering of dynamic distributed systems. In this paper, we explore how aspects and reflection have been utilised in both the programming language and middleware communities; building upon this work, we identify four core relationships that form the basis of our model for aspect-oriented reflective middleware. We then explore the potential of this model to i) increase support for the engineering of dynamic reconfigurations, and ii) improve the performance of adaptive systems.