Non-functional requirement

In systems engineering and requirements engineering, a non-functional requirement (NFR) is a requirement that specifies criteria that can be used to judge the operation of a system, rather than specific behaviours. They are 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, because they are usually architecturally significant requirements.[1]

In software architecture, non-functional requirements are known as "architectural characteristics". Note that synchronous communication between software architectural components, entangles them and they must share the same architectural characteristics.[2]

  1. ^ Chen, Lianping; Ali Babar, Muhammad; Nuseibeh, Bashar (2013). "Characterizing Architecturally Significant Requirements". IEEE Software. 30 (2): 38–45. doi:10.1109/MS.2012.174. hdl:10344/3061. S2CID 17399565.
  2. ^ Fundamentals of Software Architecture: An Engineering Approach. 2020. ISBN 978-1492043454.