Teams produce 80‑page specs that nobody reads. Length kills adoption. Vague language such as “the system should be user‑friendly” leaves developers guessing. Over‑specifying details like button colours before the architecture is validated wastes effort. The result is a document that sits in a folder while the code drifts away from the original intent.
An SRS captures WHAT the system must do and the constraints it must obey. It does not describe HOW to build it. Architecture diagrams, technology choices, and deployment topologies belong in a separate design document. Keeping the two artifacts distinct prevents scope creep and lets each audience focus on its concerns.
Every requirement must be specific, testable, unambiguous, traceable, and feasible. Replace “the API must be fast” with “the API must respond in under 200 ms for 95th‑percentile requests”. A test can verify that metric. One interpretation only eliminates disputes. Link each line to a business need or user story so changes can be assessed so impact analysis is possible. Feasibility means the team can deliver it within budget, timeline, and technical constraints.
User stories capture intent: “As a warehouse manager, I want to scan a barcode to update inventory so that I don’t manually type quantities.” Formal requirements capture constraints: “The barcode scanner integration must support Code 128 and QR formats at a minimum 300 dpi resolution.” Both are useful. Neither replaces the other. Stories give context; requirements give measurable criteria.
Functional requirements describe what the system does: create an order, send an email, display a report. Non‑functional requirements describe how well it does it: performance, security, availability, scalability, compliance. Most projects treat non‑functionals as optional and accumulate technical debt. Write them with the same rigour as functional ones. “The system shall encrypt data at rest using AES‑256” is testable. “The system shall be secure” is not.
Every requirement needs acceptance criteria — the conditions under which the requirement is satisfied. Without them, “done” is ambiguous. For the API latency requirement above, acceptance criteria might read: “Automated load test simulating 1,000 concurrent users returns 95th‑percentile response time ≤ 200 ms on the staging environment.” If the test passes, the requirement is met. If it fails, it isn’t.
The happy path is usually obvious. The SRS must answer: what happens when the user is offline, the API returns 503, the payload is malformed, the session expires mid‑form, the database deadlocks? Document these scenarios explicitly. Developers implement what is written; they rarely invent error handling that isn’t specified.
Requirements change. Track every change: who changed what, when, and why. A requirement document with no version history is untrustworthy. Use Git or a requirements tool with audit trails. Tag baseline versions at each review gate. When a stakeholder asks why a rule exists, the history answers instantly.
Requirements need review from business stakeholders (is this what you need?), developers (is this buildable?), and testers (can we test this?). All three. A review that skips testers produces untestable specs. A review that skips developers produces fantasy specs. Schedule a formal walkthrough with all parties present. Capture decisions and action items in the version history.
A working SRS for a medium‑complexity project is 5–20 pages, not 80. Use tables for requirement lists — ID, description, priority, acceptance criteria, traceability link. Write in plain language. Replace prose process descriptions with flow diagrams. A diagram communicates a workflow in seconds; a paragraph takes minutes to parse and is easier to misinterpret. Store the document in the same repository as the code so it versions alongside the implementation.
Ship the SRS. Build the software. Keep the document current. That is the entire job.