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Design Documentation

The discipline of writing a design down, revising it under review, and stating its own risk plainly — carried to revision 16, 26 and 35 on the largest programmes.

Also known as Architecture Decision Records, Design Review

Design documents in this record are not artefacts produced after the fact. They are the mechanism by which a design is reviewed, argued over and approved, and their revision numbers are the evidence.

The Duval County Courthouse network design ran to 262 pages at revision 16 by the time it was executed. The consolidated CAD/911 dispatch design carried through thirty-five revisions and a review with the Florida Department of Law Enforcement. The enterprise Palo Alto firewall architecture reached twenty-six revisions over its life. The Annex data centre consolidation ran on three documents at revisions ten, twelve and ten, each with its own drawing set, test plan and back-out plan.

The overview of the data centre consolidation stated plainly that redundancy would be reduced for a period, and what was being done about it. A design document that hides its own risk is worth less than no document.