The customer establishes requirements usually as a result of some operational need—that is, some need the organization has for improving its capability, competitiveness, or dominance in a particular area. Requirements often are the result of the organization's strategic objectives and may be driven by the company's need to improve or change its core business.
A specific requirement is something a product (or service) must do or a quality the product must have. Any requirement exists primarily because the customer wants the product to have the particular functionality or quality. A requirement also can exist simply because the product type demands certain functions or qualities. For example, to be truly functional, a product that is used in testing might need to be self-aligning or self-calibrating to a preset tolerance. Hence, a secondary requirement to self-align is inherent in the product's functional capability because of the primary requirement to test rapidly, often, and accurately.
Most of us can readily accept that a product must have certain functional requirements, but many of us don't realize that there also are nonfunctional requirements. Understanding the different types of requirements is crucial to identifying and planning to meet them.