Methods of Measuring Software Reuse for the Prediction of Maintenance Effort

Abstract

A major difficulty in evaluating the costs of reusing software is determining the amount of reused software artefacts in systems. Determining the amount of reuse in a system is important for software maintenance because reused software is likely to need less corrective maintenance than newly developed software. Reusing software can also decrease costs of testing and integration. In this paper, we describe some practical techniques for measuring the amount of software reuse using simple tools. The goal is to provide accurate assessment of the state of existing software systems in order to assess quality and deploy resources efficiently. The techniques for software developed on the UNIX system use the standard utilities ‘find’ and ‘diff’. Software developed under configuration management by the ‘sccs’ utility is measured using the ‘prs’ utility. Techniques are also given for measurement of the amount of reuse in software that was developed on personal computers. Each of the methods was used for reuse measurement at NASA’s Goddard Space Flight Center. The methods were applied to measure reuse in moderately large software systems used for ground centre control of spacecraft.