Differences in types of software maintenance work: an empirical study

One aspect of the software maintenance process, the generation of changes to the maintained software, is addressed. The software product is situated in the context of its process and environment. It is suggested that there are two broad categories of changes to software: those that are product induced and those that are environmentally induced. The differences between these categories are examined. A description is given of the software system which provided the data, the data themselves and their analysis to verify the hypotheses formulated. The data are examined globally, first for all the subsystems, then for only the old ones and finally for only the new ones. Possible uses and extensions of the simple exponential decay model, which is the best of those fitted to the data, are discussed