Incremental Development is based on use cases or use case flows which define working pieces of functionality at the user level. In an increment, the models required to develop a working software increment are each incremented until a working, tested executing piece of software is produced with incremental functionality. This approach:

	Improves estimation, planning and assessment. Use cases provide better baselines for estimation than traditionally written specifications. The estimates are continuously updated and improved throughout the project.
	Allows risks to the project to be addressed incrementally and reduced early in the lifecycle. Early increments can be scheduled to cover the most risky parts of the architecture. When the architecture is stable, development can be speeded up.
	Benefits users, managers and developers who see working functionality early in the lifecycle. Each increment is, effectively, a prototype for the next increment.