4. The interchange document is Atlas's own schema
- Date: 2026-08-02
- Status: accepted
- Where it is written down: issue #5 §5.1, §10 decision 6; generate.md §1
Context
The reference implementation's interchange document is mgdoc — MapGenie's
shape. Every other translator impersonates it: a source that has nothing to do
with MapGenie must first pretend to be MapGenie in order to be composed. The
capture archive inherited the same flavour in its naming. That is a data
source's vocabulary sitting at the centre of a format that is supposed to be
source-neutral.
Decision
No data source's shape, vocabulary, or name may appear outside its own
internal/ directory.
internal/ defines the Atlas interchange document, designed
backwards from what composition needs — worlds, lenses, collections, features,
geometry, attributes, provenance — with no source's shape privileged. MapGenie
becomes an ordinary translator into it.
The capture archive is a source-neutral concept the generate lane owns and documents: content-addressed captures, per-source id-space bits, the same-slug policy. The existing on-disk archive is kept verbatim as input data — years of captured history are data, not code — read through its legacy layout; nothing new inherits its naming.
Consequences
- A document is produced and consumed inside one run. It is not an archive
format, nothing is expected to read one back in five years, and
atlas translateprints one so the two halves of the lane can be reasoned about separately. - The translator fixtures pin source semantics; they are reference material and regression tripwires, not byte gates, because equivalence is judged at the composed-bundle level.
- Curation moves out of code into reviewed data files, and a client that speaks a standard protocol is parameterized by data — so a new dataset on a known protocol is a configuration entry rather than a new client.
- Each source's registry entry carries license and attribution, which the workbench's source cards surface.