# The projection

One job: the envelope contract, and its proof. The envelope is a conformant superset
of the standard's event — extension fields ride under a declared JSON-LD context, and
`project(event)` always validates against the pinned official EPCIS 2.0.1 schema. One
half of that sentence without the other is not the claim.

## The declared context

An envelope document declares its extension namespace in `@context`, beside the
standard's own:

```json
"@context": [
  "https://ref.gs1.org/standards/epcis/epcis-context.jsonld",
  { "spine": "https://epcis.dev/ns/spine/v1" }
]
```

Every extension field is prefixed (`spine:who`, `spine:activity`,
`spine:warrantedBy`, …), so a standard EPCIS 2.0 consumer reads the document as what
it is: a standard document carrying declared, namespaced extensions — not a fork.

## project() — and the proof

`project(event)` returns the event with the envelope removed: a plain EPCIS 2.0
event. The contract is not "usually validates" — the capture pipeline refuses any
event whose projection does not validate, so nothing enters the record that cannot
leave it conformant. Executed 2026-07-31 against the published package, on the
fixture that carries the fullest envelope in the corpus:

```
$ CORPUS=node_modules/epcis.dev/golden-corpus
$ npx epcis.dev validate --project --json \
    $CORPUS/valid-superset/object-event-full-envelope.json
{
  "valid": true,
  "schema": {
    "artefact": "epcis-json-schema.json",
    "version": "2.0.1",
    "sha256": "0f46ff694efffd8d8ce840a33dfde84228add11b516b8b258f3200740ae210af"
  },
  "errors": []
}
$ echo $?
0
```

The verdict names the artifact and the digest it judged against — the pinned official
GS1 schema, the same sha256 published on [/conformance/](/conformance/) and returned
by the live door at `POST /validate` on this origin.

## What projection removes is enumerable

Projection is lossy by design, and the loss is exactly the envelope: the
per-dimension diff on [the event](/docs/event-model/the-event/) shows `spine:who` and
`spine:activity` lifting off while all five standard dimensions survive untouched.
Nothing else moves — `project()` never rewrites, reorders or "fixes" standard fields.
The library export is the same function the CLI and the doors run:

```js
import { project, validateEpcis } from "epcis.dev";
```

---

**Proof, not adjectives.** This build could not verify the gateway's test suite green, so no sentence on this page claims a passing run — the last verified run is recorded in the repository's own CI, not here. Live on this origin, no key: POST /translate, /validate, /hash. No conformance attestation has ever been issued. The dated ledger is /what-ships-today/.