Poor Definition of "Requirement"

Karl Wiegers, author of several books on product requirements, says his favorite definition of requirement is:

"Requirements are…a specification of what should be implemented. They are descriptions of how the system should behave, or of a system property or attribute. They may be a constraint on the development process of the system."

This unfortunate definition comes from Ian Sommerville and Pete Sawyer.

Frequent readers of this blog know that I find this definition to be overly broad. After all "a specification of what should be implemented" could include a detailed design specification with UML class and collaboration diagrams. Wieger's favorite definition thus fails to provide any meaningful distinction between requirements and design.

A proper definition of requirement must clearly distinguish between requirements and design.

Comments

Unknown said…

Agreed. A good requirement is a statement of the problem, that can be solved, and absent a design of how to solve it.

See my article "On Reqs and Specs" for more. http://www.pragmaticmarketing.com/publications/topics/09/on-reqs-and-specs/

Mon Mar 14, 11:14:00 AM 2011

Roger L. Cauvin said…

Thanks, Steve. Your "On Reqs and Specs" is highly recommended, and I think it hits the nail on the head. It's nice that one of the most respected authorities in the product management community has drawn attention to this issue.

Mon Mar 14, 12:25:00 PM 2011

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