Functional and Non-Functional requirements

During the requirements gathering phase of the project, we’ll be categorising the requirements we generate against a set of broad areas. This will make it easy to locate requirements for particular aspects and to ensure that we are suitably covering all of the anticipated angles. This post is a brief introduction to the categories of requirements, which themselves are divided into Functional and Non-Functional requirements.

Functional Requirements

A Functional Requirement is one which specifies the operation of the system(s)

  1. functionality: the scope of functionality of the solution
  2. performance: how the solution performs
  3. interoperability: how the parts of the solution interact with each other and the outside world
  4. hardware: implications for the hardware/server aspects of the solution
  5. software: implications for the software aspects of the solution
  6. standards: any relationships to standards (either formal or de facto)
  7. scalability: how the solution is intended or designed to cope with increases in scale of data and usage
  8. flexibility: how the solution will adapt to different use cases

Non-Functional requirements

A Non-Functional Requirement is one which is qualitative and helps define the boundaries of the solution

  1. usability: relating to the usability and/or accessibility of a solution
  2. ease of adoption: relating to the ease by which the solution can be adopted
  3. strategic: relating to strategic information and/or decisions
  4. ethical: relating to support for ethical issues
  5. legal: ensuring compliance or related to legal issues
  6. business flexibility: supporting the business side of the sector and ensuring that it is responsive/adaptive
  7. resourcing: how to resource the solution and/or related organisational change
  8. governance: how the governance aspects of a solution are specified
  9. transition management: relating to the process of adopting a solution
  10. business sustainability: relating to how the requirement helps sustain the business side of the sector
  11. business scalability: how the requirement helps the business side of the sector scale up
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