thesis - Faculty of Information and Communication Technologies ...

Chapter 3. Data Selection Methodology
tems, 1057 unique versions and approximately 55000 classes (in total
over all the various systems and releases). Our data comprises three
broad types of software systems: (a) Applications, (b) Frameworks, and
(c) Libraries. In our selection, we aimed to select a similar number of
systems for each of the types.
Applications are software systems that can be considered stand-alone
and tend to perform a specific set of tasks. Examples from our data
set include a Bit-torrent client, a role playing game, an image editor,
and a text editor. These systems often tend to have a graphical user
interface component. Frameworks and Libraries, on the other hand
are systems that provide generic/reusable abstractions with a well defined
API. There is one key distinction between a framework and library.
Frameworks tend to impose a much stricter flow of control in the program.
However, when we classified the systems, we used the terminology
that has been used by the development team. So, if a development
team classifies their system as a framework, we use the same term.
Examples of frameworks in our data set are the Spring framework (an
inversion of control framework) and Hibernate Object Relational mapping
framework. Some of the libraries that we investigated are popular
XML processors like Apache Xerces and Saxon. A full list of all of the
systems is provided in Table 3.3, and the meta data that we capture
for each system is presented in Appendix A. Our data set contains 14
Applications, 12 Frameworks and 14 Libraries.
A set of projects in our data (for instance Hibernate, Spring Framework,
Acegi and Saxon) though open source, are developed by engineers that
get paid for their effort as these projects are managed by commercial
(for-profit) enterprises. All of these systems originally started as traditional
open-source projects and over time adopted business models that
generate revenue while the source code is still made available under a
range of open source licenses. We tagged a system as commercially
backed based on information provided on the project web site which
indicated the name of the sponsoring company and the developers that
work for that entity.
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