Factoring Differences for Iterative Change Management

An approach for factoring source-code differences is presented. A single large difference between two versions of a program is decomposed into factors (i.e., smaller changes). The application of all the factors is equivalent to the application of the single large difference. The factors are obtained by user-defined criteria. They include changes that are limited to a specific syntactic construct or ones that occur throughout a file. The factors can be applied individually or in combination to generate intermediate forms of the large change. This directly supports iterative software change management by decomposing large changes into smaller factors. The approach uses srcDiff, an XML representation of multiple versions of a source-code file and their differences. XML transformations are used to factor a change according to an XPath expression. The approach is applied to changes made to a large opensource system. The results indicate the approach is flexible and efficient, and can be integrated with common differencing tools.