Architectural Description and Review
When designing the architecture for a Greenfield system, you periodically perform architectural reviews to determine whether it can deliver the user's requirements. For a legacy system, you know it works (even if it has issues) but you need to determine how it works. Even with documentation, there is likely to be a gap between that and reality. You start with two extra important pieces of information, which are the real stakeholders and artefacts of the running system itself.
The International Standard for "Systems and software engineering — Architecture Description" is ISO42010. I will be using the terminology and processes from this standard where possible. Don't let this panic you! This is a lightweight standard and imposes no restrictions on your processes or development methodology. When creating a Greenfield Architectural Description, you will (usually) perform the following steps:
Identify stakeholders
Identify stakeholder's concerns
Identify functionality...
