Functional and non-functional solution requirements

From the VCAA glossary:

Functional requirements (what the solution is required to do)

Non-functional requirements of the solution (solution attributes) such as:

• user-friendliness
• response rates
• robustness
• portability
• reliability
• maintainability

A requirement is a need of what a particular product or service should be or perform. It identifies a necessary attribute, capability, characteristic, or quality of a system that a user finds valuable and useful.

Requirements are often determined during the analysis phase of the Problem Solving Methodology (PSM) and end up being documented in a system's logical design.

A Functional Requirement specifies something that the delivered system must be able to do.

A Non-functional requirement specifies something about the system itself, and how well it performs its functions, e.g. usability, availability, reliability, supportability, testability, maintainability, and ease-of-use.

A good list of requirements (i.e. a logical design) does not say how the requirements should be achieved. Such matters are left to the system designer during the design phase of the PSM. Describing how the system should be implemented may be known as implementation bias or "solution engineering".

Also see: Collecting information during analysis

Also see: The PSM