The 3 levels of requirements

Traditionally people talk about three levels of requirements.

You can think of it as a sort of heirarchy descending from the strategic goals of the organisation to the physical implementation of tools and processes.

• Business Requiremets
• Functional Requirements
• System Requirements

Here is a concise article explaining the concept. Note it adds a fourth level to the front - market drivers for change. This article describes the four levels of requirements, gives a view on who should 'own' each level and how they are usually modelled or documented - "The Requirements Hierarchy" Posted April 30, 2007 by John Mansour

And here is a similar article with a slightly different view at Search Software Quality; What Are Requirement Types Jan 01, 2008 by Roxanne Miller.

And there is my post on this topic from a week or two ago.

Lastly, don't forget non-functional specifications. Often a neglected area, this is where many projects have trouble delivering.

Project Management
Business Analyst
Picture from Steffe at Flickr