de l’information
The fact that few classes have NOC values greater than zero indicates that most classes in the system
are leaf classes. Overall, 76 of the classes had a DIT value greater than zero, indicating that they are
subclasses. The remaining 98 classes are at the root of the inheritance hierarchy. The above makes
clear that the inheritance hierarchy for this system was “flat”. Variable DIT has a small variation, but this
is primarily due to there not being a large amount of deep inheritance in this framework. Shallow
inheritance trees, indicating sparse use of inheritance, have been reported in a number of systems thus
far [27][30][32].
Figure 4: Box and whisker plots for all the object-oriented product metrics. Two charts are shown to
allow for the fact that two y-axis scales are required due to the different ranges.
The LCOM values may seem to be large. However, examination of the results from previous systems
indicate that they are not exceptional. For instance, in the C++ systems reported in [22], the maximum
LCOM value was 818, the mean 43, and the standard deviation was 106. Similarly, the system reported
in [19] had a maximum LCOM value of 4988, a mean of 99.6, and standard deviation of 547.7.
4.2 Correlation with Size
Table 4 shows the correlation of the metrics with size as measured in LOC. As can be seen all of the
associations are statistically significant except DIT. But DIT did not have much variation, and therefore a
weak association with size is not surprising. All metrics except LCOM and NPAVG have a substantial
correlation coefficient, indicating a non-trivial assocation with size.