one pinned row per scheme — reference, not narrative

The scheme registry.

Grammar, check-digit rail, canonical form, symbology bindings, enrichment rails with license class, and the join rule into events and transactions. Every page is backed by the same row as machine data at /schemes/<scheme>.json.

GTIN — Global Trade Item Number

The GTIN registry row: four lengths, one 14-digit identity; GS1 mod-10; symbology bindings; license-clean enrichment rails.
GS1 Application Identifiers — the payload grammar

The AI grammar row: fixed vs variable termination, GS separators, AIM symbology prologues, date and decimal AI semantics — a pinned table, not folklore.
GS1 Digital Link — the URI form

The Digital Link registry row: the URI grammar from the path down, canonical and compressed forms, and the conformant resolver semantics behind it.
GLN — Global Location Number

The GLN registry row: thirteen digits naming a party or a location, one mod-10 rail, and the three-layer join — EDI N1 loops, EPCIS party lists, Peppol endpoints.
SSCC — Serial Shipping Container Code

The SSCC registry row: eighteen digits naming one logistic unit, the mod-10 rail, AI (00), and the custody join into AggregationEvents.
VIN — Vehicle Identification Number

The VIN registry row: seventeen characters, the fully published check-digit rail (ISO 3779 / 49 CFR 565.15), and public-domain decode rails.
ISBN — a valid GTIN-13 in 978/979

The ISBN registry row: ISBN-13 as a GTIN-13, the ISBN-10 mod-11 rail and 10→13 conversion, and the honest license posture on book enrichment.
UDI — Unique Device Identification

The UDI registry row: one FDA regime, three issuing agencies' grammars (GS1, HIBCC, ICCBBA), the DI/PI split, and CC0 enrichment with GMDN stripped.
NDC — National Drug Code

The NDC registry row: three 10-digit layouts, the 11-digit billing canonicalization, an honest "check": "none", and the GTIN embedding behind the "3" prefix.
Tracking numbers — a scheme family, not a scheme

The tracking registry rows: USPS IMpb with its published Pub 199 MOD10 rail, UPS 1Z as consensus parse with a typed best-effort label, FedEx as parse-and-say-so.
DL/ID (AAMVA PDF417) — parse and verify, never store

The AAMVA registry row: the PDF417 license barcode parsed and verified locally, with hard policy flags — no_retention, enrich refused — as registry data.