The metric calculation is based on the following article and calculates the class connectivity.
PhD Thesis: Monitoramentodemetricasdecodigo-fonteemprojetosdesoftwarelivre by Paulo Roberto
Miranda Meirelles.
See the adaptation of the paragraph about Afferent Connections per Class in the article:
Measures the connectivity of a class. If a class "Ci" access a method or attribute of a class "Cj",
consider "Ci" a client of the supplier class "Cj", denoting "Ci => Cj". Consider the follow function:
client(Ci, Cj) = 1, if (Ci => Cj) and (Ci != Cj)
client(Ci, Cj) = 0, otherwise.
So "ACC(Cj) = (sum(client(Ci, Cj)), i = 1 to N)", where "N" is the total number of system classes. If the
value of this metric is large, a change in the class has substantially more side effects, making
maintenance more difficult.