Page "Functional decomposition" Paragraph 5

where is some other function.

Decompositions of this kind are interesting and important for a wide variety of reasons.

In general, functional decompositions are worthwhile when there is a certain " sparseness " in the dependency structure ; that is, when constituent functions are found to depend on approximately disjoint sets of variables.

Thus, for example, if we can obtain a decomposition of into a hierarchical composition of functions such that,,, as shown in the figure at right, this would probably be considered a highly valuable decomposition.