thesis - Faculty of Information and Communication Technologies ...

Chapter 1. Introduction
Given that change is inherent within an active and used software system,
the key to a successful software evolution approach lies not only in
anticipating new requirements and adapting a system accordingly [87],
but also in understanding the nature and the dynamics of change, especially
as this has an influence on the type of decisions the developers
make. Changes over time lead to software that is progressively
harder to maintain if no corrective action is taken [168]. Compounding
this, these changes are often time consuming to reverse even with
tool support. Tools such as version control systems can revert back to a
previous state, but they cannot bring back the cognitive state in the developer’s
mind. Developers can often identify and note local or smaller
changes, but this task is much more challenging when changes tend
to have global or systemic impact. Further, the longer-term evolutionary
trends are often not easily visible due to a lack of easy to interpret
summary measures that can be used to understand the patterns of
change.
Software engineering literature recommends that every time a software
system is changed, the type of change, the design rationale and impact
should be appropriately documented [219, 257]. However, due to
schedule and budget pressures, this task is often poorly resourced, with
consequent inadequate design document quality [50, 97]. Another factor
that contributes to this task being avoided is the lack of widespread
formal education in software evolution, limited availability of appropriate
tools, and few structured methods that can help developers understand
evolutionary trends in their software products. To ensure that all
changes are properly understood, adequately explained and fully documented,
there is a need for easy to use methods that can identify these
changes and highlight them, allowing developers to explain properly the
changes.
Given this context, where we have an evolving product, there is a strong
need for developers to understand properly the underlying growth dynamics
as well as have appropriate knowledge of major changes to the
design and/or architecture of a software system, beyond an appreciation
of the current state. Research and studies into how software
evolves is of great importance as it aids in building richer evolution
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