Empirical study of software maintenance tasks

An empirical study of software maintenance tasks was carried out in a large Norwegian organization in the period 1992-93. More than one hundred randomly selected maintenance tasks were studied through interviews with the maintainers performing the tasks immediately before they started the tasks and immediately after they had completed the tasks. The collected data is used to develop distributions and to test 33 hypotheses about software maintenance. The findings from the study indicate, for example, that: Application system documentation plays only a minor role as maintenance information source. The maintenance productivity, measured in LOC/effort, is predicted by the size of the task and type of change in the source code, but seems rather independent of language level, maintainer experience, application age and application size. There is an economy of scale for software maintenance tasks. The type of programming language does not correlate with proportion of unexpected maintenance problems, task complexity or task size. The proportion of corrective maintenance decreases with increasing age of the application.