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Chapter 6. Change Dynamics
portion of the code from the previous versions. The second re-write
abandoned much of the code base and started on top of another opensource
project. This level of fluctuation, and continuous change effectively
meant that developers did not have sufficient time to increase the
maturity of the project as it was consistently undergoing substantive
changes.
Although a higher degree of violations of these change properties does
not imply a poor quality software system, consistent and repeated violations
can indicate an unusual phase within the project which may
required additional attention or appropriate documentation to properly
communicate the state of the project to all stakeholders. This type of
summarised information is often masked in software project due to the
large volume of changes that take place, and because of a lack of empirically
derived heuristics.
6.3.2 Rate and Distribution of Change
Modifications are unavoidable as systems are maintained. However,
very few of the classes tend to experience a high level of modification.
Of the classes that have changed, most have been touched a few times –
only a small proportion is modified several times. This modification profile
is very similar in all systems under analysis, suggesting that most
classes in a system tend to reach a stable state very quickly. Combined
with our earlier observation that a good proportion of code is never
touched between releases, this suggests that development teams tend
to create a stable set of abstractions very quickly. Our findings provide
further support to a similar conclusion reached by Kemerer et al. [148]
based on an analysis of maintenance logs.
Although our approach does not reveal the actual amount of code that
has changed, it provides us with a broad indicator. One of the systems
that has resisted changes was Wicket, a web application development
framework. Interestingly, the rate of modification in Wicket was close to
many other systems. However, the observed distribution of these modifications
suggests that most of the changes were minor fixes. At the
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