Week 8 / Sixth Lecture : Identifying Needs and Establishing Requirements. [WeeFong]

A requirement is a singular documented physical and functional need that a particular product or service must be or perform. It is most commonly used in a formal sense in systems engineering, software engineering, or enterprise engineering. It is a statement that identifies a necessary attribute, capability, characteristic, or quality of a system for it to have value and utility to a user.

Projects are subject to three sorts of requirements:

• Business requirements describe in business terms what must be delivered or accomplished to provide value.
• Product requirements describe properties of a system or product (which could be one of several ways to accomplish a set of business requirements.)
• Process requirements describe activities performed by the developing organization. For instance, process requirements could specify specific methodologies that must be followed, and constraints that the organization must obey.

Types of product requirements

Requirements are typically placed into these categories:

• Architectural requirements describe what must be done by identifying the necessary system architecture of a system
• Functional requirements describe the functionality that the system is to execute; for example, formatting some text or modulating a signal. They are sometimes known as capabilities.
• Non-functional requirements describe characteristics of the system that the user cannot affect or (immediately) perceive. Nonfunctional requirements are sometimes known as quality requirements or ilities.
• Constraint requirements impose limits upon the design alternatives or project/process operations. No matter how the problem is solved the constraint requirements must be adhered to.