Modern product development techniques recognize that it is very unusual for all product requirements to be known and fixed before development can be started. In fact most products are part of a phased program of successive releases where features are constantly added and defects corrected. This is a move from a waterfall model to an iterative development technique

By their very nature requirements have to be managed in different ways over the project lifecycle. In the early stages collections of ideas are explored as candidates for a release while an analysis is carried out to define the implications, costs, risks and other aspects. At this point it is important to remain flexible and agile for change. As the development cycle progresses it becomes more difficult and expensive to make changes so requirements definitions need to become progressively more rigid. In most companies there are specific rules in the workflow for each development phase.

Iterative requirements management depends upon the ability of systems engineers to extract requirements from multiple sources and stakeholders. Requirements are then analyzed and associated with design articles such as hardware items or software modules. Those articles are themselves then analyzed and a design created based on components and submodules with associated lower level requirements. Requirements management and iterative systems design go hand in hand; a complete product value chain from customer interface can be created based on links and is often depicted as a "V" model.

 

When selecting requirements management tools it is important to make sure of the following points are covered:

• the tool should be flexible and support multiple workflows
• workflows should be linked to the stage of the project lifecycle
• version control and approval routing should be supported
• users should have the ability to define their own fields as necessary
• there should be a capability to enter diagrams which often contain requirements as well as plain text
• there should be a possibility to link requirements, features, test cases and defects either within the tool itself or externally to 3rd party tools
• ideally there should be provision to link requirements to other collaboration artifacts such as meeting minutes and risk records
• requirements should be grouped into a hierarchical structure with tree navigation
• It should be possible to generate reports of requirements which become automatically generated specifications.