Reifying Design Patterns to Facilitate Systems Evolution

Abstract

In the Web age systems must be increasingly flexible, reconfigurable and adaptable in addition to being developed rapidly. As a consequence, designing systems to cater for change is becoming critical to their success. Allowing systems to be self-describing or description-driven is one way to enable this. To address the issue of evolvability in information systems, this paper proposes a pattern-based description-driven architecture. The proposed architecture embodies four pillars – firstly, the adoption of a multi-layered and reflective meta-level architecture, secondly, the identification of four modeling relationships that must be made explicit to be examined and modified dynamically, thirdly the identification of five patterns which have emerged from practice and have proved essential in providing reusable building blocks, and finally the encoding of the structural properties of these design patterns by means of one pattern, the Graph pattern. A practical example of this is cited to demonstrate the use of description-driven data objects in handling system evolution.