A set of requirements is complete when it describes all significant concerns of the user – functionality, performance, design constraints, attributes, and external interfaces. If any of these are missing, the requirements are incomplete.
There’s no single right way to develop detailed specifications, just as there’s no single right programming language for every application. Different projects demand different techniques. Requirements managers need a mix of skills to adapt to whatever circumstances they’re working in.
This is the process I follow on projects. It’s not fancy, but it works for me. Defining the requirements. Write down what needs to be built. Be specific. Ambiguous requirements are the root cause of most problems later on. Approval. Get sign-off on the requirements before anything else. If the requirements change later, that’s fine, but do it deliberately, not by accident. Template designs. Work out the structure and layout before writing code. For web projects this means mockups and wireframes. For other projects it means architecture diagrams and data models. Template approval. Get the designs signed off too. It’s cheaper to change a design than to change code. Coding. Build it. Internal release. Get it in front of the team first. Internal testing catches the obvious stuff before anyone external sees it. Testing. Proper testing, not just “I clicked through it once.” Automated tests where possible, manual where necessary. Alpha release. Early access for a small group. Expect bugs. The goal is to find them in a controlled environment. Beta release. Wider release. More users, more edge cases. This is where you learn what people actually do with the software versus what you thought they’d do. Project goes live. Production. The real world. The key thing is not to skip steps. I’ve seen projects that jump straight from requirements to coding and then spend three times as long fixing problems that a proper design phase would have caught.