A requirement defines the specific use case and attributes of a new feature.
The domain model defines the following characteristics for requirements:
Any number of requirements may be aggregated into collections.
Requirements may be created in response to Requirement Change Requests.
Requirements are versioned.
A requirement can be related to other requirements.
Requirements may be related to any number of test requirements, from the test management system.
Requirements may be related to any number of development change requests, from the development management system.
There may be many types of requirements. Out of the box, a requirement can be classified as a business requirement, a system requirement, or a design requirement.