Versioned survey releases
A published release never changes. A correction is issued as a new release that supersedes the last, so a client can always say which version they reviewed, measured and downloaded.
A published release is frozen
Immutability is enforced by the database rather than by the application, on every path into it apart from a statutory erasure. A published release may make exactly one transition — to superseded — and its identity, its checksum, its dates and the record of where it came from cannot be altered even then.
The files under a release are frozen with it. What a client downloaded is what was published, and nothing rewrites it in place.
A correction is a new release
Supplementary runs, revised layouts and corrections are all issued the same way: publish again. The new release becomes the current one and the previous release is marked superseded, kept exactly as it was.
A worked example
A boundary survey is published on 3 March as release 1 and delivered that afternoon. On 11 March a missed control point is corrected and the survey is published again as release 2. Release 1 is now superseded and is still, byte for byte, the survey the client reviewed on the third — and the receipt from that delivery still names its checksum.
The dates and the survey in this example are illustrative.
Review work sits over the release, not in it
Measurements, saved work items, notes and discussions belong to the people reviewing, and are drawn over the release. Nothing a reviewer does changes what was published: a design proposal is explicitly a preview over an immutable release, and publishing again is the only act that produces a new version.
What leaves as evidence
- An export carries the release it was taken from and the moment it was taken. Where it contains a computed volume or profile it also carries the notice that it is a planning estimate and not a certified survey document, so a figure cannot be quoted onward without it.
- A delivery receipt names the release and its checksum, which is what ties a downloaded file back to a specific published version months later.
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