# Protocol and Rail Catalog

Extensibility catalog for additional rails. **New rails require a completed doc derived from [_rail-template.md](_rail-template.md) before merge.**
 Adapters are added incrementally; each defines identifier types, endpoint profiles, capability taxonomy, and optional connector in `packages/connectors/`.

## Implemented

- **AS4 / PEPPOL** — See data-model identifier types; SMP/SML connector spec in docs/architecture/connectors.md.
- **ISO 20022 over AS4 (FI-to-FI)** — [iso20022-over-as4.md](iso20022-over-as4.md). PartyId (BIC, LEI) → endpoint + cert + AS4 profile; Service/Action for pacs/camt; directory-only (no ISO 20022 parsing, no settlement). Scheme-specific profiles: [iso20022-scheme-profiles.md](iso20022-scheme-profiles.md) (TARGET2, Fedwire, CHAPS).
- **SS7** — e164, gt, pc, ssn; GTT via routing artifacts.
- **Card networks** — [cards.md](cards.md); pan.bin, BIN table, ISO8583.
- **DTC / Digital securities** — [dtc.md](dtc.md); lei, bic, dtc.participantId, dtc.accountId.
- **KTT** — [ktt.md](ktt.md); placeholder rail.

## Candidate Families (priority order)

- **Payments:** ISO 20022 over AS4 (FI-to-FI) documented; ISO 20022 over API, SWIFT, Fedwire-like remain candidates.
- **EDI / B2B:** AS2, SFTP EDI, RosettaNet.
- **Healthcare:** HL7 MLLP, FHIR endpoints (endpoint registry + certs).
- **Identity:** DID, DNSSEC, PKI directories.
- **Message brokers:** Kafka topics, NATS subjects, AMQP queues (logical addresses + ACL).

Integration: add identifier validators in core, register profile in protocol_registry, optional connector; document in a new docs/protocols/*.md.