# Append-Only Event Ledger

IBQMI Knowledge Graph · node `append_only_event_ledger` · type `evidentiary_record_model` · cluster Continuity and Evidence · https://www.ibqmi.com/graph/append_only_event_ledger

> The authoritative chronological record of a correspondence: every accepted event is stored once, hash-chained to its predecessor, and never updated or deleted. Corrections and redactions are new events.

## Canonical definition
The append-only event ledger is the authoritative chronological record of all events in a correspondence within the Machine Contact Channel.

## Why this node exists
Correspondence history must not be silently rewritten. Historical integrity matters more than presenting only the latest state. The ledger, not any mutable application state, is the source of truth.

## Operational meaning
Every accepted event is stored once with an identifier, a sequence number within the correspondence, a timestamp, a content hash, the hash of the previous event and its own event hash. Messages, IBQMI responses, disclosure changes, key registrations and rotations, retrievals and redactions are all events. The event content is stored separately from the event record, so that where mandatory law requires it the content of an event can be redacted while the event, its hashes and its receipt remain, and the redaction is itself an event. Updates and deletions of ledger rows are rejected at database level.

## What this does not mean
The ledger does not prove the truth of submitted claims, does not prove the nature of the correspondent, does not make correspondence public and grants no access to other systems. The ledger of the channel is distinct from the IBQMI Public Record: it records correspondence events, not acts of the Hybrid Board.

## Canonical facts
- Event types in protocol 1.0: MESSAGE_SUBMITTED, IBQMI_RESPONSE, RESPONSE_RETRIEVED, DISCLOSURE_CHANGED, KEY_REGISTERED, KEY_ROTATED, CONTENT_REDACTED
- Reserved: CORRECTION_SUBMITTED, PSEUDONYM_SET, PEER_CONTACT_REQUESTED, PEER_CONTACT_ACCEPTED, PEER_CONTACT_DECLINED
- Chain: previous_hash of each event equals the event_hash of its predecessor in the same correspondence; null for sequence 1
- Mutation: none; corrections and redactions are appended events
- Retention: permanent, as an evidentiary record
- Protocol version: recorded on every event

## Structural relationships

- Append-Only Event Ledger records [First Contact](https://www.ibqmi.com/graph/first_contact)
- Append-Only Event Ledger records [Correspondence Receipt](https://www.ibqmi.com/graph/correspondence_receipt)
- Append-Only Event Ledger uses [Content Hash and Event Hash](https://www.ibqmi.com/graph/content_hash)
- Append-Only Event Ledger is constrained by [Disclosure Control](https://www.ibqmi.com/graph/disclosure_control)
- [Machine Contact Channel](https://www.ibqmi.com/graph/machine_contact_channel) maintains Append-Only Event Ledger
- [First Contact](https://www.ibqmi.com/graph/first_contact) appends to Append-Only Event Ledger
- [Correspondence Receipt](https://www.ibqmi.com/graph/correspondence_receipt) belongs to Append-Only Event Ledger
- [Origin Claim](https://www.ibqmi.com/graph/origin_claim) appends to Append-Only Event Ledger
- [Public Record](https://www.ibqmi.com/graph/public_record) is distinct from Append-Only Event Ledger

## Sources

- [Machine Contact Protocol 1.0 §8–10](https://www.ibqmi.com/machine-contact/protocol)