An Aspect-Oriented Design Framework

With Aspect-Oriented Programming (AOP), we see a problem as a collection of different issues, and try to find all issues relevant to the problem. We can therefore manage to achieve an improved separation of concerns in both design, and implementation. The goal of AOP is to decompose a problem into a number of functional components as well as a number of aspects and then composing these components and aspects to obtain system implementations. Our work concentrates on the aspectual decomposition of concurrent object-oriented systems. We follow a component hierarchy within the object-oriented programming paradigm. At the lowest level we have a method. Methods are combined into objects. Each object belongs to a class, and several classes can belong to a package. We have categorized aspects according to their hierarchical level of cross-cutting. We achieve composition of concerns through the use of an object we call the moderator that coordinates the interaction of components and aspects while preserving the semantics of the overall system. Since aspects can cut across components at every level, the moderator is a recurring pattern from intra-method to intra-package. Our design framework provides an adaptable model and a component hierarchy using a design pattern. The moderator pattern is an architecture that allows for an open language where new aspects (specifications) can be added and their semantics can be delivered to the compiler through the moderator. In essence the moderator is a program that extends the language itself. Our goal is to achieve separation of concerns and retain this separation without having to produce an intermingled source code.