thesis - Faculty of Information and Communication Technologies ...

Chapter 6. Change Dynamics
stance, in Saxon, the developers choose to implement both compiletime
and run-time handlers for XSL-T instructions in the same component
[144], they also share memory mapped data structures among different
components, increasing the inter-dependencies, which has been
shown to increase certain types of defects [130]. Unfortunately, the exact
rationale for these choices in Saxon has not been explicitly stated
(our inference is that the choice to merge compile-time and run-time
handlers in Saxon may have been motivated by a desire to improve the
performance).
The architecture guide provided with Axis [11] states that most modules
are not functionally separated and attempt to provide a diverse range
of functionality, this tight coupling is noted by the developers as an
known concern that needs to be addressed in later releases [11]. The
developers of Axis, interestingly, do suggest a potential solution that can
address the coupling issue in the architecture document [11] but these
recommendations have not been implemented (at time of analysis). The
decisions that the iText team made with respect to compiling are similar
to choices made for Axis and Saxon as inferred from the change logs and
release notes [128].
Another aspect common in iText and Saxon was the choice made by the
developers to build their own collections data structures (such as a List,
Map and Queue) that underwent many changes when they were initially
introduced into the code base. Comments provided in the source
code suggest that the motivation for creating their own collections data
structure was to improve performance. It is possible that at the time
of development the developers did not have access to reliable and mature
high-performance collections classes such as those that exist freely
now like GNU Trove [280] and the Google collections framework [107].
Though, reliable high-performance collections libraries now exist the
developers have left their original data structures and algorithms intact.
In iText, Saxon and Axis developers made a number of incremental modifications.
Unfortunately, without an underlying architecture and design
that allowed them to incrementally meet the specifications, they
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