The Reference Model

Before storing anything, anarchie has to understand it. anarchie's rm module is a native Rust model of the openEHR Reference Model with a canonical JSON reader and writer. Two features fall straight out of it and are useful on their own, without a repository.

Get the example Composition

This walkthrough uses one small canonical Composition, a single blood-pressure reading. The repository ships it at examples/vitals.json; copy it into the CDR you just created (from my-cdr, the clone's examples/ is one level up):

cp ../examples/vitals.json .

Everything below assumes vitals.json is in the current directory.

Inspecting a Composition

Point anarchie info at any canonical-JSON Composition and it parses the whole tree and summarises it:

anarchie info vitals.json

Composition: Blood pressure
  archetype:  openEHR-EHR-COMPOSITION.encounter.v1
  template:   vital_signs_encounter.v1
  rm_version: 1.1.0
  language:   en
  territory:  GB
  category:   event
  composer:   Dr Ada Lovelace
  content items: 1
  sections:      0
  entries:       1
  elements:      2

Those counts come from an actual tree-walk of the Reference Model: Sections recurse, Observations descend into their events, and Elements are counted at the leaves. If the file is not a structurally valid Composition, info fails with a clear error rather than guessing.

Canonicalising

anarchie canonicalise reads a Composition and re-emits it in anarchie's canonical JSON form:

anarchie canonicalise vitals.json > vitals.canonical.json

This matters because openEHR defines a canonical serialisation: two systems that serialise the same Composition should produce byte-comparable output. That property is the foundation everything else rests on:

• Diffable. Canonical files diff cleanly, so a meaningful change in the data produces a meaningful change in the file.
• Hashable. Equal Compositions hash equal, so de-duplication and integrity checks are trivial.
• Stable in git. Re-committing unchanged content produces an identical file, so the only thing that changes between two versions is what actually changed.

Next: The Git-backed Store