On Measurement and Analysis of Software Changes

Software becomes better or worse because of the changes made to it. Each change to legacy software is expensive and risky but it also has potential for generating revenues because of desired new functionality or cost savings in future maintenance. Hence it is important to understand and quantify change properties in order to make good business decisions. Particularly good sources of historical information about changes, especially for legacy software, are generated by change management systems used by most large software organizations. This paper describes how to measure change properties and how to use that information to identify cost and quality drivers in software production. The methodology is codiied in a system called SoftChange. SoftChange was developed for use with the 5ESS TM switch at Lucent Technologies , but can also be used with other software projects using the same, widespread version control systems. SoftChange deenes, constructs and presents essential measures of software change size, complexity, and developer expertise. Also, it provides tools for imputing the purpose and eeort required for a change, and generates predictions of the quality of a change. This methodology uses measurements of changes to beneet the software development process and to generate insights about software evolution.