A life-cycle cost viewpoint of software maintainability

The dynamic and ever-changing characteristics of software requirements make life-cycle costs for today's software very expensive. The cost of post-operational maintenance and modification often exceeds the original development cost. Software which is easily modifiable is not built naturally; it must be carefully contracted for and the development of modifiable software, its support tools and its documentation, must be judiciously managed and tested. However, without resorting to technological innovation of R&D investment, there is much that can be done well within today's state-of-the-art to accommodate significant life-cycle cost savings provided that the acquisition agencies understand the issues and are willing to spend the required time and effort (money) during the software development phase. In this paper we propose a procedure-based approach to software engineering of modifiability by discussing a number of important issues such as contracting for modifiability; techniques for building modifiability into software; planning for post-delivery test facilities and support tools; software maintenance documentation; planning and review to assure that the product evolved support modifiability.