What are we looking at?
In what document, and with what structure, should we record requirements so the team can work from them with confidence?
In system design, having a formal and precise document for recording requirements is vital. This document tells every member of the team exactly what the system is meant to do, what limits it has, and how its success is measured.
What is an SRS?
An SRS (Software Requirements Specification) is a formal document that specifies all the functional and non-functional requirements of a software system. It is the bridge between stakeholders, analysts, designers, programmers and testers, and if the bridge isn’t built well, the project goes wrong.
Recommended structure
1. Introduction. The purpose of the document, the scope of the system, the definition of key terms, and references to other documents.
2. Overall description. The overall view of the system, users and actors, general constraints (platform, language, regulations), and assumptions and dependencies.
3. Functional requirements. For each function: a title, a description, inputs and outputs, the actors involved and a priority (low, medium, high). It is better for this section to be numbered and precise, such as 3.1 User registration, 3.2 Login, 3.3 Sending a message.
4. Non-functional requirements. Security (encryption, authentication), performance (response time, capacity), usability, maintainability and extensibility, and availability.
5. System interfaces. Interfaces to other systems, APIs and communication standards, databases or files.
6. Acceptance criteria and validation. How do we know a requirement has been implemented correctly? What tests are designed for it?
Writing tips
- Use simple, precise, unambiguous language
- Each requirement must be measurable, not vague or subjective
- Classify and prioritise requirements
- Tables, diagrams and use cases help clarity
- The document must be updatable and reviewable throughout the project
A simple sample for recording a functional requirement:
| ID | Requirement | Description | Actor | Input | Output | Priority |
|---|---|---|---|---|---|---|
| FR-01 | Login | The user enters a username and password and enters the system | User | Username, password | Dashboard | High |
I think the SRS is the project’s road map. If the analyst writes it precisely, comprehensibly and keeps it up to date, the design and development teams can move ahead with confidence.