Fig. 14.1.2 The application environment.The functional decomposition is the depiction of the functions that will be achieved by a
system. The functional decomposition is laid out in a hierarchical fashion. At the top of
the decomposition is the general function of what is to be accomplished by the system. At
the second level are the main functions of what is to be accomplished. Then, each second
level function is broken down into its subfunctions, until the point of basic functionality is
reached.
The functional decomposition is useful to see what the different activities of a system will
be. It is useful for organizing the functions, identifying overlap, and checking to see if
anything is left out. When you are setting out on a long trip, it is useful for looking at a
map of the United States to see what states you will visit and the order in which the states
will be traveled.
After the functional decomposition is completed, the next step is to create data flow
Chapter 14.1: Data Models Across the End-State Architecture