A requirement is a singular documented need of what a particular product or service should be or perform. It is a statement that identifies a necessary attribute, capability, characteristic, or quality of a system in order for it to have value to a user. Requirements show what elements and functions are necessary for your project.
A list of requirements is often used in the vendor selection process to evaluate suppliers, clarify business needs and make them explicit. A requirements list plays an important part in an RFP.
Product and process requirements
We distinguish between three sorts of requirements:
- Business requirements describe in business terms what must be delivered or accomplished to provide value.
- Product requirements describe the properties of a system or product.
- Process requirements describe activities performed by the supplier. For instance, process requirements could specify specific methodologies to be followed, and constraints that the organization must obey.
Functional and non-functional requirements
A functional requirement is a description of what a system must be able to do. They describe the functionality that the system is to execute; for example personalizing a newsletter or synchronizing with a CRM system. They are sometimes known as capabilities.
Non-functional requirements specify something about the system itself, and how well it performs its functions. They are also known as ‘performance requirements’ or ‘quality of service requirements.’ Examples of such requirements include usability, availability, reliability, supportability, testability, maintainability, and ease-of-use.
Constraints impose limits upon the alternatives or project/process operations. No matter how the problem is solved the constraint requirements must be met.