Requirements are a key topic in the quality engineering domain. A requirement is a statement identifying a capability, physical characteristic, or quality factor that bounds a product or process need for which a solution will be pursued. The requirement development (also known as requirements engineering) is the process of producing and analyzing customer, product, and product-component requirements. The set of procedures that support the development of requirements, including planning, traceability, impact analysis, change management, and so on, is known as requirements management. There are two kinds of software requirements:

• Functional requirements are actions that the product must do to be useful to its users. They arise from the work that stakeholders need to do. Almost any action such as, inspecting, publishing, or most other active verbs can be a functional requirement.
• Non-functional requirements are properties, or qualities, that the product must have. For example, they can describe properties such as performance, usability, or security. They are often called quality attributes.

Another important topic strongly linked with the requirements is the specification, which is a document that specifies in a complete, precise, verifiable manner, the requirements, design, behavior, or other characteristics of a system, and often the procedures for determining whether these provisions have been satisfied.