Software Cost Reduction Methods in Practice.

Sixty percent of the software costs associated with the design, development, and implementation of computer systems occurs in the maintenance phase. A significant reduction in the maintenance costs can be realized with a design for change philosophy integrated into the engineering life cycle. By carefully identifying the expected changes to a system and rigorously applying the concepts of information hiding and abstraction of interfaces, the changeable aspects of a system can be isolated. In 1978, a Software Cost Reduction program was initiated whose goal was to apply these 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 Parnas and associates. This paper extends that approach by updating the methodology based upon 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. Finally, a summary provides our impressions of the methodology and its potential to reduce system maintenance costs. [ABSTRACT FROM AUTHOR]