thesis - Faculty of Information and Communication Technologies ...
thesis - Faculty of Information and Communication Technologies ...
thesis - Faculty of Information and Communication Technologies ...
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Chapter 2. S<strong>of</strong>tware Evolution<br />
[59, 100, 101, 103, 127, 193, 204, 217, 239, 254, 277, 304, 310] focused<br />
on a few popular <strong>and</strong> large s<strong>of</strong>tware systems (for example, the Linux<br />
operating system or the Eclipse IDE).<br />
Interestingly, evolution studies that have consistently investigated many<br />
different s<strong>of</strong>tware systems (in a single study) are change based studies.<br />
Change based studies tend to use the revision logs generated <strong>and</strong><br />
maintained by the configuration management tools rather than collecting<br />
data from individual releases in order to analyze the dynamics<br />
within evolving s<strong>of</strong>tware systems [25]. A few notable large change based<br />
studies are Koch et al. [152, 153] who studied 8621 s<strong>of</strong>tware systems,<br />
Tabernero et al. [118] who investigated evolution in 3821 s<strong>of</strong>tware systems<br />
<strong>and</strong> Capiluppi et al. [39] who analysed 406 projects.<br />
Given the small number <strong>of</strong> systems that are typically investigated in release<br />
based evolution studies, there is a need for a comparatively larger<br />
longitudinal release based s<strong>of</strong>tware evolution study to confirm findings<br />
<strong>of</strong> previous studies still hold, to increase the generalizability <strong>of</strong> the findings,<br />
<strong>and</strong> to improve the strength <strong>of</strong> the conclusions. Even though previous<br />
release based studies [59, 100, 101, 103, 127, 193, 204, 217, 239,<br />
254, 277, 304, 310] have investigated a range <strong>of</strong> different s<strong>of</strong>tware systems,<br />
a general limitation is that there has been no single study that<br />
has attempted to analyze a significant set <strong>of</strong> s<strong>of</strong>tware systems. Our<br />
work fills this gap <strong>and</strong> involves a release based study <strong>of</strong> forty s<strong>of</strong>tware<br />
systems comprising 1057 releases. The focus on a comparatively larger<br />
set <strong>of</strong> s<strong>of</strong>tware systems adds to the existing body <strong>of</strong> knowledge since<br />
our results have additional statistical strength than studies that investigated<br />
only a few s<strong>of</strong>tware systems. Our data set selection criteria <strong>and</strong><br />
the method used to extract information is discussed in Chapter 3 <strong>and</strong><br />
Chapter 4, respectively.<br />
2.3 The Laws <strong>of</strong> S<strong>of</strong>tware Evolution<br />
The laws <strong>of</strong> s<strong>of</strong>tware evolution are a set <strong>of</strong> empirically derived generalisations<br />
that were originally proposed in a seminal work by Lehman<br />
<strong>and</strong> Belady [168]. Five laws were initially defined [168] <strong>and</strong> later ex-<br />
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