SRS (Software Requirements Specification)
Definition
The SRS is a formal document that completely describes what the software system will do (and, importantly, what it will not do), serving as the contract/agreement between customer and developer, and the baseline for design, coding, and testing.
Purpose of SRS
- Provides a single source of truth for all requirements
- Serves as a basis for cost/schedule estimation
- Forms the legal/contractual agreement between client and development team
- Baseline for validation and acceptance testing
- Communication bridge between customer, analyst, designer, and tester
Typical Contents of an SRS
- Introduction — purpose, scope, definitions, references, overview
- Overall Description — product perspective, product functions, user characteristics, constraints, assumptions
- Specific Requirements
- Functional requirements
- Non-functional requirements
- External interface requirements (UI, hardware, software, communication)
- Appendices — supporting information, glossary
- Index
Characteristics of a Good SRS
- Correct — accurately reflects actual needs
- Unambiguous — single interpretation
- Complete — all requirements included
- Consistent — no conflicting statements
- Ranked for importance/stability
- Verifiable — testable
- Modifiable — easy to update
- Traceable — each requirement can be traced to its origin and to design/test
Who Uses the SRS
| Role | Use |
|---|---|
| Customer | Verify the system will meet their needs |
| Project Manager | Estimate cost, schedule, resources |
| Designer | Basis for system/architecture design |
| Tester | Basis for writing test cases |
| Maintenance team | Understand original intent for future changes |
Exam tip: Know the SRS structure (Introduction, Overall Description, Specific Requirements) and the "good SRS" characteristics list — both are extremely common exam questions, often asked together with the IEEE SRS Standard topic.