Donald Bren School of Information and Computer Sciences

Enormous resources are invested in the construction of software. As needs change we would like to be able to preserve these investments. In this paper we outline a unified model for addressing the problem of change in software systems for which the original specifications are not available. Our approach is derived from a much broader paradigm for software construction. The approach is based on recovery of abstractions and design decisions made during implementation of the current version of a system. The paper consists of two major parts. We begin with a discussion of the Draco paradigm for software construction and how it can be applied to maintenance and porting problems. We follow with a discussion of our experience with a porting project using prototype implementation of these ideas.