Functional Analysis and Decomposition

At the top level, systems are normally described by the functions they are to perform in distinction to specific subsystems and components. For example, the functions of a command, control, and communications system may be described by the following selected functions:

• Communications

• Computation

• Identification

• Surveillance

By maintaining a focus on function, rather than the manner in which the function is to be executed in hardware, software, and human components, we allow the systems engineer to consider a host of alternative ways of implementing a given function. We explicitly separate the ''what'' is to be done from the ''how'' it should be done. We consciously want to avoid leaping to a premature conclusion regarding a specific way to implement a given function. Selecting such specific ways is represented by the tasks of detailed design.

The basic steps under this element of systems engineering involve the following:

• Definition of the top-level functions of the system

• Decomposition of the preceding into lower-level functions and subfunctions

• Allocation of generic information and data flows among and between functions and subfunctions

• From the requirements analysis and allocation element, assuring that all requirements are allocated to the functions and subfunctions

The preceding steps are specifically related to the system architecting process and also set the stage for subsystem design once the architecture is developed. As such, they are considered further in Chapter 9.

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Project Management Made Easy

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