thesis - Faculty of Information and Communication Technologies ...

Chapter 3. Data Selection Methodology
The size and skill of development teams, though helpful, was a criteria
that was removed after an initial pass at selecting systems mainly because
it was not possible to obtain this information accurately. In some
of our projects, the software used to host the source control repositories
changed during the evolutionary history of a project and many projects
choose to archive older contribution logs at regular intervals removing
access to this data. These aspects limited our ability to determine the
number of active and contributing developers to the project, specifically
during the early part of the evolution. Another facet that could not be
accurately determined was that the level of contribution from different
developers. That is, we were not able to identify reliably if some developers
contribute more code than others. Further, some project members
contributed artwork, documentation, organised and conducted meetings
while some focused on testing. These non-code contributions were
often not visible as active contributors on the source code repository.
Another interesting finding during our investigation was that developers
that have not contributed any material code for many years are still
shown as members in the project. These limitations, including an observation
that suggests that a small sub-set of developers are responsible
for a large amount of the changes and additions to the source code
in open source software, has been noted by Capiluppi et al. [39].
The observation that few developers contribute most of the code by
Capiluppi et al. [39] and the variance in the contribution levels over
time indicates that we require a measure that can meaningfully identify
the number of normalised developers working on a project at any
given point in time. However, such a metric has not yet been developed
and widely accepted as effective and hence we did not rely on the
development team size as a variable for use in our study.
3.5 Selected Systems - An Overview
Using the selection criteria, we initially identified 100s of software systems
that satisfy the criteria. However, we focused on a representative
smaller subset in order to allow us to study each of the selected systems
at a greater depth. Our final data set comprises of forty software sys-
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