thesis - Faculty of Information and Communication Technologies ...

Chapter 4. Measuring Evolving Software
Abbv. Name Description
SCC Super Class Counted as 0 if super class is
Count java.lang.Object, else 1.
NOC Number of Count of classes that directly inherit from this
Children class. Metric value is in the interval [0, N).
NOD Number of Count of all classes that inherit from this
Descendantitance
class. Computed by walking down the inher-
tree. Metric value is in the interval
[0, |N| − 1).
DIT Depth in If the class has no parent in core software
Inheritance
Tree
system then the value is 1, otherwise it is
1+depth of inheritance of direct parent.
Table 4.6: Inheritance metrics computed for each class.
l out (n) = l e out(n) + l i out(n) (4.5.5)
The dependency metrics collected for each class and the abbreviation
used for the metrics are presented in Table 4.5. While determining
the dependencies between classes we ignore all dependency links into
java.lang.Object since all objects in Java inherit from this class. By
ignoring this default link we are able to determine if there are classes
that do not have any outgoing links to other objects, that is, Out-Degree
Count can be zero for some classes. Furthermore, having a potential
zero value for the dependency metrics simplifies the statistical analysis
that we undertake in our study (discussed in further detail in Chapter 5
and Chapter 6).
We illustrate how our dependency metrics are computed by using an
example class diagram (see Figure 4.7 showing both the figure and the
metrics computed, and Table 4.5 presents the full form of the abbreviations
used). In this thesis, we consider the dependency metrics that
we extract to be a measure of structural complexity since they capture
the degree of inter-connectedness between classes (as discussed earlier
in Section 4.2.2).
87