Functional specification
Functional specification is a document that describes the needs and expected features of a software project from a usage standpoint, without prescribing a technical solution. It acts as a shared reference between the client and the development team, framing scope, priorities and success criteria.
What a functional specification contains
A solid functional specification covers:
- Context and goals: the business problem to solve;
- Scope: what is included, and what is not;
- Features: described as use cases or user stories;
- Constraints: regulatory, technical, schedule;
- Acceptance criteria: how completion is validated;
- Indicative budget and timeline.
Functional vs technical specification
| Functional | Technical | |
|---|---|---|
| Answers | The what and the why | The how |
| Content | Needs, usage, business rules | Architecture, technologies, system constraints |
| Written by | The business side | The technical team |
Questions fréquentes
It aligns client and provider on the real need before development, reduces misunderstandings and scope creep, and serves as the reference to validate the result. It is an investment that significantly lowers project risk.
On the client side, usually a project manager or business owner. A good provider supports this scoping exercise, since the quality of the document drives the project's success.
Yes, but it becomes a living document. Instead of a frozen spec, you frame an initial vision and scope, then refine features iteration by iteration through the backlog.
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