Posted by tac_admin, February 13, 2012

Business vs. Functional Requirements vs. Non-Functional Requirements

One of my YouTube subscribers asked for an explanation of difference between functional and system requirements so I expanded on a previous post about business and functional requirements to also include an explanation of non-functional (system) requirements.

Business vs. Functional Requirements vs. Non-Functional Requirements

Business Requirements document WHAT the business need is.

Functional requirements further describe HOW the business requirements should be accomplished.

  • WHAT
    • Accept a customer payment
  •  HOW
    • Accept payment via Web
    • Accept payment via Phone
    • Accept payment via Mail

Why do we not include how the process is performed in business requirements?

  • You may end up going down the wrong path for a solution
  • You don’t want to limit yourself to what the solution could be

A technical/system (non-functional) requirement is a requirement that describes specifically how the business problem will be solved. It reflects the view from the technical world.

  • Hardware descriptions – Are there specific types or brands of hardware that must be used?
  • Software descriptions – What development tools will be used, what programming language?
  • Database design and data conversion requirements
  • Design flows – Diagrams and descriptions that depict how programs and other system components interface with each other.
  • Programming considerations – Creating reusable modules, following standard programming naming conventions, using consistent call sequences.
  • Interface requirements describe connections between this system and other existing systems. These include interfaces, and communication mechanisms for hardware and other software systems.

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