---
id: capability.wiki.federation-models
name: Selectable Federation-Model Taxonomy
summary: Federation as a plural, composable coordination axis (fork+journal, VCS-replication+ping, query-time graph-join, feed, activity-streams, engine-mirror) selected per space.
owner: shard-wiki
status: draft
domain: helix_forge
tags: [wiki, federation, taxonomy, composable, shard-wiki]

maturity:
  discovery:
    current: D4
    target: D6
    confidence: high
    rationale: >
      A six-model taxonomy distilled from a ~23-system synthesis, each model anchored in a
      real system, with capability prerequisites and per-space/per-shard composition rules.
  availability:
    current: A0
    target: A4
    confidence: low
    rationale: >
      Designed and specified (FederationArchitecture T17) but not implemented; informational
      reuse only today.

external_evidence:
  completeness:
    level: C1
    name: Sparse
    confidence: low
    basis: scope_vs_intent_and_consumer_expectations
    satisfied_expectations:
      - the model taxonomy and selection/composition rules are documented
    broken_expectations:
      - no federation transport is implemented yet
    out_of_scope_expectations:
      - mandating a single federation mechanism
  reliability:
    level: R0
    confidence: low
    basis: consumer_quality_signals
    known_reliability_risks:
      - design-stage; no runtime evidence

discovery:
  intent: >
    Treat federation as selectable and composable rather than one mechanism, so each space
    picks fork+journal, VCS-replication, query-join, feed, activity-streams, or engine-mirror.
  includes:
    - the six federation models + their capability floors
    - per-space selection and per-shard composition
  excludes:
    - imposing one homogeneous federation network
  use_cases:
    - "shard-wiki UseCaseCatalog UC-26, UC-31, UC-33, UC-71, UC-72, UC-74, UC-79"

availability:
  current_level: A0
  target_level: A4
  current_artifacts:
    - "shard-wiki/spec/FederationArchitecture.md (T17)"
  consumption_modes:
    - informational

relations:
  depends_on:
    - capability.wiki.shard-orchestration
    - capability.wiki.coordination-journal

evidence:
  documentation:
    - "shard-wiki/spec/FederationArchitecture.md"
    - "shard-wiki/research/260614-shard-spectrum-synthesis/findings.md"

consumer_guidance:
  recommended_for:
    - planning a federation strategy that mixes models per source
  not_recommended_for:
    - implementation reuse today (design-stage)
  known_limitations:
    - no transport implemented; informational planning reuse only
---

# Selectable Federation-Model Taxonomy

Federation is plural and composable: fork+journal (Federated Wiki), VCS-replication+ping
(ikiwiki), query-time graph-join (Wikibase SERVICE), feed aggregation, activity streams
(ActivityPub), and engine-mirror (Wiki.js). A space selects a model and composes per shard;
the default is fork+journal over git. Design-stage capability — strong for planning reuse.

## Assessment notes

### Discovery
FederationArchitecture T17, distilled from the shard-spectrum synthesis (v3).

### Availability
Specified, not implemented — informational reuse only.