thesis - Faculty of Information and Communication Technologies ...

Chapter 2
Software Evolution
How does software change over time? What constitutes normal change?
Can we detect patterns of change that are abnormal and might be indicative
of some fundamental issue in the way software is developed?
These are the types of questions that research in the field of software
evolution aims to answer, and our thesis makes a contribution towards
this end. Over the last few decades research in this field has contributed
qualitative laws [174] and insights into the nature and dynamics of this
evolutionary process at various levels of granularity [41, 59, 65, 71, 85,
96, 100, 118, 127, 162, 171, 188, 194, 200, 284, 289, 289, 290, 292–294,
304]. In this chapter we present the background literature relevant for
this thesis and provide motivation for our research goals.
2.1 Evolution
Evolution describes a process of change that has been observed over a
surprisingly wide range of natural and man-made entities. It spans significant
temporal and spacial scales from seconds to epochs and from
microscopic organisms to the electricity grids that power continents.
The term evolution was originally popularised within the context of
biology and captures the “process of change in the properties of populations
of organisms or groups of such populations, over the course of
generations” [84]. Biological evolution postulates that organisms have
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