Design document review, versioning, and sign-off before build
Key Takeaway
Before the build starts, stamp the functional specification document (FSD) and the technical specification document (TSD) with a date and a version number, then get customer sign-off. The signed versions are the one official set of requirements. When the team develops iteratively, updated documents go through these steps again before the build that depends on them.
Writing the design documents is not the last step before building. The team reviews the documents, stamps them with a date and a version number, and gets the customer to sign off. Sign-off locks in one official set of requirements, so the team and the customer agree on what will be built. Scope changes found along the way are handled through change orders, which also need customer sign-off.
The FSD and the TSD
Two specification documents carry the design. The functional specification document (FSD) describes what the solution does, from the user's point of view. The technical specification document (TSD) is its sister document. The TSD describes how the solution does it, with the precise technical details needed to build what the FSD describes.
The TSD serves two audiences. The development team builds from it. The technical support team uses it to understand the implementation details.
The TSD also holds the system integration plan, which maps out how and when each external system interacts with the new solution.