World Library  
Flag as Inappropriate
Email this Article

Non-functional requirements

Article Id: WHEBN0021704165
Reproduction Date:

Title: Non-functional requirements  
Author: World Heritage Encyclopedia
Language: English
Subject: Software testing, Requirements analysis, Requirement, Digital asset management, Business analyst, NFR, Performance engineering, URPS, FURPS, Risk breakdown structure
Collection:
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Non-functional requirements

In systems engineering and requirements engineering, a non-functional requirement is a requirement that specifies criteria that can be used to judge the operation of a system, rather than specific behaviors. This should be contrasted with functional requirements that define specific behavior or functions. The plan for implementing functional requirements is detailed in the system design. The plan for implementing non-functional requirements is detailed in the system architecture.

Broadly, functional requirements define what a system is supposed to do and non-functional requirements define how a system is supposed to be. Functional requirements are usually in the form of "system shall do ", an individual action of part of the system, perhaps explicitly in the sense of a mathematical function, a black box description input, output, process and control functional model or IPO Model. In contrast, non-functional requirements are in the form of "system shall be ", an overall property of the system as a whole or of a particular aspect and not a specific function. The systems' overall properties commonly mark the difference between whether the development project has succeeded or failed.

Non-functional requirements are often called qualities of a system. Other terms for non-functional requirements are "constraints", "quality attributes", "quality goals", "quality of service requirements" and "non-behavioral requirements".[1] Informally these are sometimes called the "ilities", from attributes like stability and portability. Qualities, that is non-functional requirements, can be divided into two main categories:

  1. Execution qualities, such as security and usability, which are observable at run time.
  2. Evolution qualities, such as testability, maintainability, extensibility and scalability, which are embodied in the static structure of the software system.[2][3]

Examples

A system may be required to present the user with a display of the number of records in a database. This is a functional requirement. How up-to-date this number needs to be is a non-functional requirement. If the number needs to be updated in real time, the system architects must ensure that the system is capable of updating the displayed record count within an acceptably short interval of the number of records changing.

Sufficient network bandwidth may be a non-functional requirement of a system. Other examples include:

See also

References

External links

Scientific links

  • http://www.idi.ntnu.no/grupper/su/fordypningsprosjekt-2005/eide-fordyp05.pdf

Templates and examples

  • www.csc.calpoly.edu
  • Volere Requirements Resources

Modeling non-functional properties in SOA

  • Modeling Non-Functional Aspects in Service Oriented Architecture Wada, Suzuki,Oba

Agile non-functional requirements

  • Non-Functional Requirements: Do User Stories Really Help?

Structural requirements

  • Measurable Structural Quality as Expression of Non-Functional Requirementsde:Anforderung (Informatik)
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.