Survey

Software Reuse
CHARLES
School

W. KRUEGER
Science, G’arnegie Mellon University, Pittsburgh, Pennsylvania 15213

of Computer

Software reuse is the process ofcreating software systems from existing software rather than building software systems from scratch. ‘l’his simple yet powerful vision was introduced in 1968. Software reuse has, however, failed to become a standard software engineering practice. In an attempt to understand why, researchers have renewed their interest in software reuse and in the obstacles to implementing it. This paper surveys the different approaches to software reuse found in the research literature. It uses a taxonomy to describe and compare the different approaches and make generalizations about the field of software reuse. The taxonomy characterizes and the way these artifacts are each reuse approach interms of its reusable artifacts abstracted, selected, speciahzed, and integrated. Abstraction plays a central role in software reuse. Concise and expressive abstractions are essential if software artifacts are to be effectively reused. The effectiveness of a reuse technique can be evaluatedin terms of cognztzue dwtance-an intuitive gauge of the intellectual effort required to use the technique. Cognitive distance isreduced in two ways: (l) Higher level abstractions ina reuse technique reduce the effort required to go from the initial concept of a software system to representations inthe reuse technique, and(2) automation reduces the effort required togo from abstractions inareuse technique to an executable implementation. This survey will help answer the following questions: What is software reuse? Why reuse software? What are the different approaches to reusing software? How effective are the different approaches? What is required to implement a software reuse technology? Why is software reuse difficult? What are the open areas for research in software reuse? Categories and Subject Descriptors: D.1.O [Programming Techniques]: