Facilitating software extension with design patterns and Aspect-Oriented Programming

Software products, especially large applications, need to continuously evolve, in order to adapt to the changing environment and updated requirements. With both the producer and the customer unwilling to replace the existing application with a completely new one, adoption of design constructs and techniques which facilitate the application extension is a major design issue. In the current work we investigate the behavior of an object-oriented software application at a specific extension scenario, following three implementation alternatives with regards to a certain design problem relevant to the extension. The first alternative follows a simplistic solution, the second makes use of a design pattern and the third applies Aspect-Oriented Programming techniques to implement the same pattern. An assessment of the three alternatives is attempted, both on a qualitative and a quantitative level, by identifying the additional design implications needed to perform the extension and evaluating the effect of the extension on several quality attributes of the application.