thesis - Faculty of Information and Communication Technologies ...
thesis - Faculty of Information and Communication Technologies ...
thesis - Faculty of Information and Communication Technologies ...
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Chapter 5. Growth Dynamics<br />
• The strength <strong>of</strong> the relationship varies across systems <strong>and</strong> versions.<br />
For example, the measures Load Instruction Count <strong>and</strong> Fan-<br />
Out Count are strongly correlated in JasperReports 0.3.0 (see Table<br />
5.2), but this relationship between Load Instruction Count <strong>and</strong><br />
Fan-Out Count is not as strong in other systems <strong>and</strong> releases.<br />
• Across all systems, the measure In-Degree Count (IDC) consistently<br />
shows the weakest correlation to other metrics suggesting that in<br />
general, the popularity <strong>of</strong> a class is not a monotonic function <strong>of</strong><br />
the other metrics. This can be seen in Figure 5.4, where the IDC<br />
metric value box plot as well as the distribution plot are significantly<br />
different to that <strong>of</strong> all other metrics. Additionally, the outliers<br />
shown in the box plot (outside the whiskers) are caused by<br />
the IDC metric in all the other measures.<br />
• Except for In-Degree Count, in 75% <strong>of</strong> the releases all other measures<br />
show moderate to high positive correlation (i.e. > 0.6) between<br />
different measures.<br />
• Load Instruction Count <strong>and</strong> Store Instruction Count are in general<br />
strongly correlated (i.e., over 0.8). This signifies that data <strong>of</strong>ten requires<br />
a pair-wise read <strong>and</strong> write. However, there was one system,<br />
rssOwl where the correlation was consistently weak. In rssOwl<br />
the correlation coefficient value between Load Instruction Count<br />
<strong>and</strong> Store Instruction Count is below 0.5 during the entire evolution<br />
history, which is well below the typical expectation <strong>of</strong> a value well<br />
over 0.8. The low correlation value observed in rssOwl was caused<br />
by many classes loading a disproportionate amount <strong>of</strong> string constants<br />
in the user interface classes as well as in classes providing<br />
internationalization support. The typical strategy employed to load<br />
large number <strong>of</strong> strings is to load the data from external resource<br />
configuration files rather than by hard coding them in the source<br />
code.<br />
Our observations suggest that there is a consistent correlation between<br />
the various internal size <strong>and</strong> internal structural complexity metrics <strong>of</strong><br />
a class. However, the popularity <strong>of</strong> a class (as measured by IDC) is not<br />
a monotonic function <strong>of</strong> its size or internal complexity indicating that<br />
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