thesis - Faculty of Information and Communication Technologies ...

Chapter 6. Change Dynamics
100%
90%
80%
% Classes (Cumulative)
70%
60%
50%
40%
30%
20%
10%
0%
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
Modification Count
Axis
Azureus
Castor
Checkstyle
Findbugs
Groovy
Hibernate
Jung
Spring
Struts
Webwork
Wicket
Saxon
Xerces
Xalan
ActiveBPEL
iText
Figure 6.5: Cumulative distribution of the modification frequency of
classes that have undergone a change in their lifetime. The figure only
shows some systems from our data set to improve readability. Systems
that are considered outliers have been shown with dotted lines
reduces non-linearly, as is shown in Figure 6.5. Further, less than 1%
of classes were modified more than 20 times (most systems in our data
set have at least 20 versions) which shows that only a small proportion
of the classes undergo repeated adjustments.
Although there is some variance between systems, most systems in our
data set have a similar profile. The range also shrinks as the modification
count increases. The data range for modification count of 2
is close to 15%, however the range falls to 7% once the modification
count reaches 4 and is less than 3% by the time we consider modification
count of over 10. This consistency across different software
systems indicates that the number of releases in the history of a software
system has a minimal impact on the number of times a class is
modified.
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