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Functional Analysis

Functional analysis is the systematic process of identifying, describing, and relating the functions a system must perform in order to to be successful. It does not address how these functions will be performed.

In the early phases of the project life cycle, functional analysis deals with:


  • The top-level functions that need to be performed by the system;

  • Where theses functions need to be performed;

  • How often they need to be performed; and

  • Under what operational concept and environmental conditions.

  • Later in these early phases, functional analysis proceeds to lower levels of the system decomposition to define the system functional design and interfaces.

In describing what must be done and not how to do it, we decouple requirements from implementation. This leaves the implementation trade spaces unbiased.

But “…decomposition cannot be found in a book or dictated by the stakeholders; the decomposition is a product of the engineers of the system and is part of the architecture design process that is attempting to solve the design problem established by the requirements. The decomposition can be carried out as deeply as needed to define the transformations that the system must be able to perform.”

Functional architecture = top-down definition of system functions.

Functional flow block diagrams = show the sequence of all functions to be accomplished by a system.

Interface Diagrams = used to develop data, function or hardware interfaces.

Timelines = add functional time requirement considerations.

Functional Analysis Development Process


Develop Funtional Architecture
Functional Flow Analysis
Functional Interface Analysis
Timeline Analysis

Functional Architecture of the system and subsystems



Functional Flow Block Diagram

Interface Diagrams

Timelines (PERT or Gantt)

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