thesis - Faculty of Information and Communication Technologies ...

Chapter 6. Change Dynamics
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Figure 6.6: Number of measures that change for modified classes. x-
axis shows the number of measures that have been modified, while the
y-axis shows the percentage of classes
6.2.3 Distribution of the Amount of Change
As software evolves, we have observed that there is a proportion of code
that changes, but the number of modifications is minimal. But what
is the magnitude of this change? Is there a typical profile for most
systems, such as the one we observe in the modification frequency?
In order to observe the amount of change, we focus on the classes in
the final version that have been modified at least once in their life cycle.
We then compute the set of measures that have changed between a
class when it was first created and its state in the final version. We use
the final version as the baseline to allow for a qualitative comparison
between versions and also to check if there is a broad pattern that is
independent of system maturity. This high-level approach allows us to
see if there is a common profile across the various systems.
Measuring only the number of metrics that change provides a size change
measure that is bounded (since the total number of metrics that can
change is fixed, in our study at 54 metrics). The bounded nature of
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