ENC-ASL-CORE-INDEX ADDENDUM: Federation Encoding

Base spec: tier1/enc-asl-core-index.md

Status: Merged into tier1/enc-asl-core-index.md

1. Purpose

This addendum defines on-disk encoding changes required to support the Federation Specification:

Domain identifiers for artifacts and index entries
Visibility flags for internal vs published state
Backward-compatible update to existing index records
Integration with existing block, segment, and tombstone layouts

It ensures deterministic reconstruction across domains while preserving index lookup semantics.

2. New Fields for Index Records

Each ArtifactIndexRecord is extended to include federation metadata:

Field	Type	Description
`DomainID`	uint32 / opaque	Unique domain identifier for the artifact. Must match the domain in which the artifact was created.
`Visibility`	uint8 (enum)	Visibility status of the artifact: `0 = internal`, `1 = published`.
`CrossDomainSource`	optional uint32 / opaque	DomainID of original domain if the artifact is imported from another domain; `NULL` if local.

Encoding Notes:

DomainID and Visibility are always present in index records, even for legacy artifacts (legacy default: internal, local domain).
CrossDomainSource is optional; present only for imported artifacts.
Existing (BlockID, offset, length) mapping is unchanged.

3. Segment Header Updates

Each segment now includes:

SegmentDomainID (uint32 / opaque): domain owning this segment
SegmentVisibility (uint8): maximum visibility of all artifacts in the segment (internal or published)
Optional: FederationVersion (uint8) to allow backward-compatible upgrades

This allows fast filtering of visible segments during lookup in federated domains.

4. Tombstone Encoding

Tombstones include DomainID and Visibility fields to ensure deterministic shadowing across domains.
Shadowing rules:
- A tombstone in domain A only shadows artifacts in domain A.
- Published artifacts cannot be accidentally shadowed by internal artifacts from another domain.

5. Block Records

No change to (BlockID, offset, length) itself; however:

Blocks supporting published artifacts are considered cross-domain safe.
Optional DomainID metadata may be stored with blocks to speed up GC and federation operations.
Addressing and segment packing rules are unchanged.

6. Lookup and Reconstruction Rules

When reconstructing CURRENT in a domain:
1. Filter segments and records by DomainID and Visibility.
2. Include artifacts with DomainID = local or Visibility = published.
3. Include imported artifacts by following CrossDomainSource.
4. Apply standard shadowing and tombstone rules per domain.
Determinism and immutability guarantees remain identical to single-domain ENC-ASL-CORE-INDEX.

7. Backward Compatibility

Legacy segments without federation fields are treated as:
- DomainID = local domain
- Visibility = internal
Lookup semantics automatically ignore artifacts from other domains until explicitly migrated.
Federation fields are forward-compatible; versioning in segment headers allows safe upgrades.

8. Normative Invariants

DomainID presence: Every index record must include a DomainID.
Visibility correctness: Published artifacts are always visible to other domains; internal artifacts are not.
CrossDomainSource integrity: Imported artifacts retain immutable reference to original domain.
Deterministic encoding: Serialization of index records and segments must be identical across platforms for the same snapshot + log.
Backward compatibility: Legacy records are interpreted safely with default federation metadata.

9. Summary

This addendum updates ENC-ASL-CORE-INDEX to support federation:

Adds DomainID, Visibility, and optional CrossDomainSource to index records
Updates segment headers for fast domain/visibility filtering
Ensures deterministic lookup, reconstruction, and shadowing rules per domain
Maintains backward compatibility with legacy segments

It integrates federation metadata without altering the underlying block or artifact encoding, preserving deterministic execution and PEL provenance.

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