Software change through design maintenance

Conventional software engineering tends to focus on a small part of the software life cycle: the design and implementation of a product. The bulk of the lifetime cost is in the maintenance phase, where one must live with the product previously developed. Presently, we have little theory and fewer tools to help us manage the maintenance activity. We contend that a fundamental cause of the difficulty is the failure to preserve design information. This results from an over preoccupation with the synthesis and maintenance of code. We offer an alternative paradigm: make the design the central focus of the construction process-get code as a byproduct; make the design the central focus of the maintenance process-preserve revised designs and get code as a byproduct. A transformational scheme for accomplishing this is presented. We call it the Design Maintenance System. The programming roles change radically from coding instances for ill defined specifications to specifiers of functionality and (compiler like) implementation methods. Specification and implementation method debugging would then become prominent activities. The design scheme and change management procedures are illustrated with a simple data processing application. We sketch an ongoing implementation