As illustrated in the end-to-end domain model (see "End-to-End Orchestrated ALM" on page 7), requirements definition happens early in a development project’s lifecycle. Ideally, requirements are defined and approved before active produce development begins; approved requirements are the basis of development change requests, which in turn determine the work to be carried out by development staff. Requirements are also the basis of test requirements, thus ensuring that the original requirements for a product are followed through to the end of a project, and validated as features are tested.