Wednesday, April 18, 2007

Nonfunctional requirements and level of specification

Name: Nonfunctional requirements and level of specification
Type: Theory
Version: 2007-04-18
Source: My friend Sven

"The higher the level of a system's requirements specification, the greater the portion of non-functional requirements."

This is, because no computer system can directly realise a non-functional requirement; it has to be broken down to a set of functional requirements. This set interacts and thereby attains (or does not attain) a certain non-functional attribute.

Sven's sentence describes a necessary characteristic of good specifications. In other words if you find a high-level spec with few or no non-functional requirements, it does not mean it is not high-level. It probably means that the author forgot to include non-functional requirements.

Also, "portion" is maybe not the correct term (he used the German "Anteil"), but I think the idea is clear.

1 comment:

Andreas Lechner said...

Interestingly, nonfunctional requirements can become functional requirements when changing the scope.
For example, usability is a typical nonfunctional requirement in the scope of the application.
From the company's point of view, the application needs to succeed in its function. Usability is an important part of realizing its function.

Manual trackback-link: Nicht-funktionale Anforderungen im Scope einer Applikation (german article)