thesis - Faculty of Information and Communication Technologies ...

Chapter 6. Change Dynamics
had to modify many classes. The developers, in effect, had to make
changes in a number of classes in new versions as they attempted to
adhere to the standards incrementally. Furthermore, the lack of coherent
reusable components and libraries, also meant that they had
to improve existing classes rather than upgrade external libraries and
components.
To ensure completeness, we investigated two other systems in our data
set that share a similarity with iText, Saxon and Axis in terms of their
functional domain. The two systems were, Xerces-2 XML processor and
Xalan XSL-T processor. Both these products also satisfy standardised
XML technology specifications developed by W3C. Interestingly, these
projects made very different choices at the start of their life cycle. The
Xerces-2 project was a complete re-write of the Xerces-1 platform, however,
for the new build, developers satisfied most of the core specification
in an initial release rather than via incremental refinement. Further,
based on the experience gained from earlier attempts, the Xerces-2
developers built a modular architecture that allowed them to make incremental
adjustments [309] to changing specifications, but the bulk
of the code remained stable. The Xalan project did not have a previous
release and knowledge base to build on top of [307]. The development
team, however, chose to create a highly modular architecture with well
defined functional boundaries that permitted incremental refinement
and the ability to replace libraries and components [308]. They also
relied on a number of existing stable libraries to provide common functionality
(unlike iText and Saxon where developers built many key data
structures and algorithms). The change analysis data suggests that
these choices have helped the team as they evolve and adapt the systems.
The development strategy and choices made by the developers has an
impact on the change profile. Despite the type of approach taken, all
five systems (iText, Saxon, Axis, Xerces-2 and Xalan) have continuously
evolved, potentially satisfying user needs. However, our study suggests
that when attempting to match formal standards, a modular architecture
built after a careful analysis of the entire specification can help
reduce the frequency and magnitude of changes. The strategy of us-
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