Editing Functional decomposition (section)

== Systems engineering ==
{{main|Functional flow block diagram}}
Functional decomposition in [[systems engineering]] refers to the process of defining a system in functional terms, then defining lower-level functions and sequencing relationships from these higher level systems functions.<ref>{{cite report |url= http://ocw.mit.edu/courses/aeronautics-and-astronautics/16-885j-aircraft-systems-engineering-fall-2005/readings/sefguide_01_01.pdf |title=Systems Engineering Fundamentals |publisher=Defense Acquisition University Press |place=Fort Belvoir, VA |date=January 2001 |page=45}}</ref> The basic idea is to try to divide a system in such a way that each block of a [[Functional flow block diagram|block diagram]] can be described without an "and" or "or" in the description.

This exercise forces each part of the system to have a pure [[role|function]]. When a system is designed as pure functions, they can be reused, or replaced. A usual side effect is that the interfaces between blocks become simple and generic. Since the interfaces usually become simple, it is easier to replace a pure function with a related, similar function.

For example, say that one needs to make a [[boombox|stereo]] system. One might functionally decompose this into [[loudspeaker|speakers]], [[amplifier]], a [[tape deck]] and a front panel. Later, when a different model needs an audio [[CD]], it can probably fit the same interfaces.