Software Engineering

10.4.1 
Functional hierarchy
The functional hierarchy conveys the transformation of software specifications into 
the essential functions (functional units) that the software product must perform to 
execute the operational or business processes. It provides traceability of the soft-
ware requirements to the initial software product design configuration.

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CHAPTER 10 
Formulating the Functional Architecture
The functional hierarchy provides a gage of the software product complexity in 
three manners:
●
  The number of levels of decomposition.
●
  The breadth of each level of decomposition.
●
  The number of fundamental functional elements (functional units) from which 
the structural design is to be derived.
The number of levels of decomposition will not be consistent throughout the 
functional hierarchy. The number of layers involved with the decomposition of 
a primary function is a good indication of the complexity of the data processing 
transaction being executed. The breadth of each level of decomposition implies the 
complexity that will be encountered during software component integration and test-
ing. The number of functional units provides an initial indication of the scope of the 
software unit design, code, and testing activity. However, this indicator will be firmly 
established as a result of the software design synthesis activity. During software 
design synthesis, common or closely coupled functional units may be combined into 
a single structural unit, thereby reducing the anticipated workload for software unit 
design, coding, and testing.