Maintaining a legacy: towards support at the architectural level

Abstract

An organization that develops large, software intensive systems with a long lifetime will encounter major changes in the market requirements, the software development environment, including its platform, and the target platform. In order to meet the challenges associated with these changes, software development has to undergo major changes as well. Especially when these systems are successful, and hence become an asset, particular care shall be taken to maintain this legacy; large systems with a long lifetime tend to become very complex and difficult to understand. Software architecture plays a vital role in the development of large software systems. For the purpose of maintenance, an up-to-date explicit description of the software architecture of a system supports understanding and comprehension of it, amongst other things. However, many large complex systems do not have an up-to-date documented softwarearchitecture. Particularly in cases where these systems have a long lifetime, the (natural) turnover of personnel will make it very likely that many employees contributing to previous generations of the system are no longer available. A need to ‘recover’ the software architecture of the system may become prevalent, facilitating the understanding of the system, providing ways to improve its maintainability and quality and to control architectural changes. This paper gives an overview of an on-going effort to improve the maintainability and quality of a legacy system, and describes the recent introduction of support at the architectural level for program understanding and complexity control. Copyright © 2000 John Wiley & Sons, Ltd.