Sixty percent of the software costs associated with the design, development and implementation of computer systems occur in the maintenance phase. Since change is intrinsic in software, a significant reduction in the maintenance costs can be realized by recognizing the evolutionary aspects of software and integrating a design for change philosophy into the engineering life cycle. By identifying the expected changes early in the definition phases, and by modularizing the system to efficiently support implementation of these changes, life-cycle maintenance costs can be reduced. The author provides an example of a design methodology, a specification process and a supporting documentation structure that provides more visibility to maintenance concerns.>

In 1978, a software cost reduction program was initiated with the goal of applying modern design and documentation principles to the development of large systems. The results of this effort have been documented in several research papers published by D. Parnas et al. (1983). The author extends that approach by updating the methodology based on lessons learned during the application of the concepts to the development of a computer-based training system. An engineering life-cycle which provides more visibility to maintenance concerns is described, and the lessons learned during its implementation are discussed. A summary provides the author's impressions of the methodology and its potential to reduce system maintenance costs.>