Degree distributions,
summarizing the connectivity of each node in a graph,
indicate the probability of finding a node with a
specified degree k [11]. Now, many OO systems have
been found to possess a “scale free” degree distribution
[11,12,13], implying that P(k) obeys a power law over
an extended range of degrees k. The existence of
heavy-tailed out-degree distributions suggests a broad
spectrum of complexities, and the existence of heavytailed
in-degree distributions implies a broad spectrum
of reuse. Hence, this parameter can be used to estimate
the overall structural complexity of a system according
to the structural entropy [14].