Reflection-Based, Aspect-Oriented Software Architecture

Abstract

The Software Architecture discipline is devoted to the study and description of structures, created by the composition of software modules. At the same time, the most important merit of Aspect Orientation is the fact that it introduces a new kind of modularization, deployed in a range of new dimensions, orthogonally to traditional models. These fields are able not only to combine, but also to complement and extend each other. They show also remarkable coincidences in some of their key concepts, such as multiple viewpoints and connectors. This paper explores their relationship, in particular from the point of view of the specification of “aspect-oriented architectures” in terms of existing Architecture Description Languages (Adls). Specifically, we consider the language $\mathcal {PIL}$ar: a reflective, process-algebraic Adl conceived for the description of dynamic architectures. It has three conceptual foundations which have also been proposed as a basis for aspect-orientation, namely reflection, superimposition and process algebras. We show how, due to the semantics of its reification relationship, $\mathcal {PIL}$ar is capable to directly describe “architectural aspects” with no need for syntactic extensions. At the same time, we suggest that the addition of these extensions could be very useful anyway. The discussion is supported by an example of a coordination aspect in $\mathcal {PIL}$ar, based on the classical Paxos Consensus algorithm.