thesis - Faculty of Information and Communication Technologies ...

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Chapter 6. Change Dynamics
100%
90%
80%
70%
% Classes
60%
50%
40%
30%
20%
10%
0%
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4
6
8
Release Sequence Number
Unchanged Modified Deleted
Figure 6.1: Change evolution in the Hibernate framework. This graph
illustrates change property captured by Equation 6.2.9.
our observations for Hibernate framework and illustrates the change
evolution.
An interesting observation was that in 12 (30%) systems, at least once
in their lifetime, we noticed the percentage of unchanged classes dropping
to zero, indicating that every class in the system was modified between
two releases. Upon closer investigation, we noticed that this was
caused by the developers modifying their package names. In Java, the
standard coding convention is to embed the organisation name within
the package name (for example, org.apache.wicket.Page indicates that
this is a project managed by Apache). When projects move between
organisations (or) get adopted by commercial sponsors they tend to rename
all classes which causes the unchanged class count to drop to
zero. Further, we also had a few instances (25 versions), where developers
renamed some of the packages, but left many with the older
names. When they partially renamed, we noticed that the number of
unchanged classes was mostly under 10%.
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