1# 4. The interchange document is Atlas's own schema23- **Date:** 2026-08-024- **Status:** accepted5- **Where it is written down:** issue #5 §5.1, §10 decision 6;6 [generate.md](../generate.md) §178## Context910The reference implementation's interchange document is `mgdoc` — MapGenie's11shape. Every other translator impersonates it: a source that has nothing to do12with MapGenie must first pretend to be MapGenie in order to be composed. The13capture archive inherited the same flavour in its naming. That is a data14source's vocabulary sitting at the centre of a format that is supposed to be15source-neutral.1617## Decision1819**No data source's shape, vocabulary, or name may appear outside its own20`internal/generate/sources/<name>/` directory.**2122`internal/generate/doc` defines the Atlas interchange document, designed23backwards from what composition needs — worlds, lenses, collections, features,24geometry, attributes, provenance — with no source's shape privileged. MapGenie25becomes an ordinary translator into it.2627The capture archive is a source-neutral concept the generate lane owns and28documents: content-addressed captures, per-source id-space bits, the same-slug29policy. The **existing on-disk archive is kept verbatim as input data** — years30of captured history are data, not code — read through its legacy layout;31nothing new inherits its naming.3233## Consequences3435- A document is produced and consumed inside one run. It is not an archive36 format, nothing is expected to read one back in five years, and `atlas37 translate` prints one so the two halves of the lane can be reasoned about38 separately.39- The translator fixtures pin *source semantics*; they are reference material40 and regression tripwires, not byte gates, because equivalence is judged at41 the composed-bundle level.42- Curation moves out of code into reviewed data files, and a client that speaks43 a standard protocol is parameterized by data — so a new dataset on a known44 protocol is a configuration entry rather than a new client.45- Each source's registry entry carries license and attribution, which the46 workbench's source cards surface.