generated from coulomb/repo-seed
tegwick
04be66161e
Fixes bug B-2. States the guarantee (read-your-writes for journal-owned coordination-canonical state; causal across the derived tier; eventual+ freshness-labelled for sharded inputs). Conflict detection+representation = core mechanism, resolution = policy. Overlay-apply-under-drift semantics (fast-forward / three-way / refuse+re-present) and journal ordering. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
615 lines
39 KiB
Markdown
615 lines
39 KiB
Markdown
# CoreArchitectureBlueprint — shard-wiki
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Status: **draft for review** · Date: 2026-06-15 · Owner: tegwick
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The whole-system architecture for shard-wiki, synthesised from `INTENT.md`, the 84-entry
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`UseCaseCatalog.md`, and the full research arc (`research/260608-*`, `research/260613-*`,
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`research/260614-*` — ~23 wiki/knowledge systems plus two cross-dive syntheses). This is the
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**core** blueprint: it defines the layers, the abstractions, and the load-bearing decisions
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that everything else implements.
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Scope relationship to the other specs:
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- **`ArchitectureBlueprint.md`** (existing) is the **authorization & history sub-blueprint**
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(the L0–L4 ladder). This document references it as the design of the cross-cutting
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authorization layer (§9) and does not restate it.
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- **`SHARD-WP-0002`** is the workplan that turns §6–§8 into
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`spec/FederationArchitecture.md` + the adapter-contract section of
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`spec/TechnicalSpecificationDocument.md`.
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- **`UseCaseCatalog.md`** is the demand this architecture must satisfy; UC references below
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are load tests, not decoration.
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---
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## 1. The thesis: *canonical vs derived* (three states)
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Everything in shard-wiki follows from one organising decision — that state comes in exactly
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**three kinds**, and only one of them is disposable:
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> **1. Sharded-canonical** — content owned by each shard (shard sovereignty).
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> **2. Coordination-canonical** — durable state *born inside shard-wiki* that encodes human
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> or cross-shard decisions and exists nowhere else: overlays (the local truth against a
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> read-only shard), curator equivalence bindings, alias tables, merge/reconciliation
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> decisions. It lives in the **Git coordination journal**.
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> **3. Derived-disposable** — everything shard-wiki *computes* from (1)+(2): the union graph,
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> equivalence index, query indexes, projections, views. It can be deleted and recomputed.
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>
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> **Canonical = sharded ∪ coordination. Derived = a pure function of canonical:**
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> `derived = f(sharded, coordination)`.
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This is the architectural form of "orchestrator, not engine." shard-wiki never *becomes* the
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source of truth; it composes sources and records the decisions it makes about them. The
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research earned the *files-canonical* half empirically — every serious system externalises its
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durable truth to files+VCS and treats the rest as derived: Logseq (DataScript index over plain
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files), ikiwiki (static HTML compiled from a git repo), Glamorous Toolkit / Lepiter (live
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views over git-versioned JSON), Pharo (Tonel/Iceberg code as git text), Jupyter teams
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(nbstripout — outputs are derived noise). The one tradition that refuses this — the Smalltalk
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**image** — is exactly the one we record as a *boundary, not a backend*
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(`research/260614-squeak-pharo-deep-dive`).
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The earlier draft of this blueprint used a two-bucket framing ("canonical at the edges,
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derived in the middle"). That was wrong by omission: it had no home for **coordination-
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canonical** state, and so contradicted itself by listing curator bindings and alias tables as
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"derived/rebuildable" when a human binding manifestly cannot be rebuilt. The three-state model
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fixes that crack (review finding A-1) and makes `derived = f(canonical)` *literally* true.
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Three consequences fall straight out, and they are the spine of the rest of this document:
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1. **Graceful degradation is free.** If the derived tier is always recomputable, a backend
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that can only be read is still a first-class participant — you just derive less from it.
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2. **Provenance is tractable.** Because shard-wiki never claims to *be* the source, every
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derived artifact can always point back to the canonical input it came from (union without
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erasure is a structural property, not a feature bolted on).
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3. **The derived tier is a pure function of canonical state.** `derived = f(sharded,
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coordination)`. Bugs in the derived tier are recoverable by recompute; only the two
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canonical tiers must be durably protected — sharded by each shard, coordination by the
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Git journal (history). *Recomputability is a correctness property of the derived tier, not
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a promise that a from-scratch rebuild is operationally cheap — see §8.4 and the
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operational-envelope axis.*
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### The dual narrow waist
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Heterogeneity is mediated at exactly two interfaces, and nowhere else:
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- **Bottom waist — the Shard Adapter Contract (§6).** Every backend, however weird, enters
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through one versioned, capability-described interface.
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- **Top waist — the Wiki Page Model (§7).** Every consumer, however demanding, sees one
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backend-neutral, Markdown-first-but-stretchable page model.
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Between the waists, core logic is written **once** against capabilities and the page model —
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never against a specific backend. Adding TiddlyWiki or Notion or a git forge is writing an
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adapter and declaring a capability profile, not editing core algorithms.
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---
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## 2. Architectural invariants
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These are non-negotiable. Violating one is a design bug, not a tradeoff. They are INTENT's
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principles fused with the research through-lines.
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| # | Invariant | Source |
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|---|-----------|--------|
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| I-1 | **Orchestrator, not engine.** Core composes shards; it never replaces or homogenises them. | INTENT Stability Note |
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| I-2 | **Three states; derived = f(canonical).** State is sharded-canonical, coordination-canonical (journal), or derived-disposable. The derived tier (union/index/projection) is a pure, recomputable function of the two canonical tiers; only canonical state is durably protected. | §1; Logseq/ikiwiki/GT through-line |
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| I-3 | **Capability-awareness is data.** A binding's abilities are a *profile* (positions on spectra), read by generic core logic — not per-backend branches. | synthesis v3 §2; INTENT capability-aware adapters |
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| I-4 | **Union without erasure.** Every page/revision/projection/overlay/view carries its provenance, freshness, liveness, and divergence. | INTENT; provenance-granularity spectrum (Wikibase) |
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| I-5 | **Overlay before mutation.** Writes to anything below write-through land as drafts/patches/MRs first; no silent remote mutation. | INTENT |
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| I-6 | **Git-addressable coordination.** Every information space has a Git-backed journal even when its shards are not git-native. | INTENT |
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| I-7 | **Mechanism over policy.** Canonical-source, conflict, editorial, sync cadence are configurable presets, never hard-coded. | INTENT |
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| I-8 | **Graceful degradation.** A limited backend is still usable as read-only / cache / projection / backup / patch target. | INTENT |
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| I-9 | **Identity ≠ placement.** A page is an entity that may occupy N locations; address by identity, not by path. | Trilium note/branch; ZigZag |
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| I-10 | **History is the floor.** Every write is a recoverable commit; recoverability, not gatekeeping, is the baseline protection. | ArchitectureBlueprint §2 |
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| I-11 | **Authorization in core, authentication delegated.** Core decides who-may; an external provider says who-is. | INTENT; ArchitectureBlueprint |
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| I-12 | **Not a file-sync daemon; not an execution platform.** Sync is wiki-page-semantic; computation is recognised+projected, not hosted. | INTENT; computational-page-model synthesis |
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---
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## 3. The layered architecture
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```
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┌───────────────────────────────────────────────────────────────┐
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│ L6 Consumers — Orchestrator API · CLI/agents · Web/Obsidian │
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├───────────────────────────────────────────────────────────────┤
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X-cut │ L5 Authorization (PEP/PDP, identity-provider iface) → │ X-cut
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Prove- │ see ArchitectureBlueprint.md (L0–L4 ladder) │ Capa-
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nance ├───────────────────────────────────────────────────────────────┤ bility
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▲ │ L4 Union & Projection (DERIVED, rebuildable cache) │ ▲
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│ │ identity resolution · equivalence/chorus · union graph · │ │
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│ │ replication+derivation projections · moldable view registry│ │
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│ │ · derived query index │ │
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│ ├───────────────────────────────────────────────────────────────┤ │
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│ │ L3 Coordination (Git journal · overlay/patch engine · │ │
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│ │ federation-model strategies · reconciliation) │ │
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│ ├───────────────────────────────────────────────────────────────┤ │
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│ │ L2 Wiki Page Model ── TOP WAIST ── │ │
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│ │ backend-neutral pages · identity≠placement · span address ·│ │
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│ │ provenance envelope · the page shapes │ │
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│ ├───────────────────────────────────────────────────────────────┤ │
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│ │ L1 Shard Adapter Contract ── BOTTOM WAIST ── │ │
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│ │ versioned iface · capability profile (15 spectra) · │ │
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│ │ attachment-mode binding · operation verbs │ │
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└──── ├───────────────────────────────────────────────────────────────┤ ──┘
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│ L0 Backends (not ours): git repos, wiki/ subdirs, Gitea/ │
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│ GitLab/GitHub wikis, folders, Obsidian, WebDAV, Notion, │
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│ Coulomb spaces, notebooks, … │
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└───────────────────────────────────────────────────────────────┘
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```
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**Provenance** and **Capability** are drawn as vertical rails because they are not layers —
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they are present at every layer. A page object at L2 carries provenance; a projection at L4
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carries provenance; an authz decision at L5 records the context under which content was read.
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Likewise a capability profile declared at L1 is consulted at L3 (can we write-through?), L4
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(can we delegate a query?), and L5 (can this principal even reach the op?).
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The dependency rule is strict and downward, and it tracks the **three states (§1)**, not the
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layer numbers: **the derived-disposable tier (the whole of L4) may be deleted and recomputed
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from canonical state (sharded content at L1 + coordination-canonical state in the L3 journal).**
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Nothing canonical may depend on derived state. Note the journal at L3 is *canonical* (it holds
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overlays, bindings, aliases, merges); only L4 is disposable.
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---
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## 4. Core abstractions (the vocabulary code must use)
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Straight from INTENT, sharpened by research. New code maps onto these; it does not invent
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parallel terms.
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- **Shard** — an independently meaningful page store attached to a root entity, with
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*sovereignty*: its own backend, capability profile, history, identity model, limits.
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- **Root entity / information space** — the joined space shards attach to; the unit of
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Git coordination and of multi-tenancy (a tenant maps to a root entity, ArchitectureBlueprint).
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- **Shard adapter contract** — the versioned L1 interface; the bottom waist.
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- **Capability profile** — a shard binding's position on each of the 15 spectra (§6) plus its
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supported verbs. *The* data structure that drives degradation.
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- **Wiki page model** — the L2 backend-neutral page; the top waist.
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- **Page identity vs placement** — a page is an entity (identity); it may have N placements
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(paths/shards). Addressing, equivalence, and transclusion key on identity (I-9).
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- **Provenance envelope** — the metadata wrapper every artifact carries: source shard,
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freshness, liveness, authorization context, overlay status, divergence, derivation lineage.
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- **Coordination journal** — the L3 Git-backed record of change flows for a space, and the
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durable home of all **coordination-canonical** state (§1): overlays, curator equivalence
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bindings, alias tables, merge/reconciliation decisions. This state is born inside shard-wiki,
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exists nowhere else, and is *not* derived — it must be committed, never recomputed.
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- **Overlay** — a non-destructive local edit against a remote/read-only/limited shard,
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representable as draft/patch/commit/MR before destructive apply. Coordination-canonical: an
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unapplied overlay is the local truth and lives in the journal.
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- **Projection** — a derived view of shard content, typed on two axes (§8): *kind*
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(replication | derivation) × *liveness* (static … irreducibly-live).
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- **Federation model** — the selected coordination strategy for a space (§ taxonomy, T17).
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- **Shard mode** — read-only · write-through · mirrored · projected · cached · canonical
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(a *policy* selection constrained by the capability profile).
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---
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## 5. Why "layered" and not "pipeline" or "plugin-bus"
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Two rejected alternatives, recorded so the choice is legible:
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- **A sync pipeline** (source → transform → sink) was rejected: it implies a privileged
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direction and a canonical sink, which violates shard sovereignty (I-1) and union-without-
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erasure (I-4). shard-wiki is a *star* (many shards ↔ one space), not a pipe.
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- **A flat plugin bus** (every backend a peer plugin emitting events) was rejected as the
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*top-level* shape: it has no narrow waist, so heterogeneity leaks into every consumer.
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We keep the plugin idea but confine it to L1 (adapters) and L3 (federation strategies),
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behind the waists.
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The layered-with-rails shape is what makes I-2/I-3/I-4 hold simultaneously.
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---
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## 6. Bottom waist — the Shard Adapter Contract (L1)
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The single most important design decision in the project: **the adapter contract models
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positions on capability spectra, not a flat checklist of boolean verbs.** A backend is not
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"can/can't merge"; it sits *somewhere* on the merge spectrum, and federation operations
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degrade by position. This is the lesson of putting ~23 systems in one matrix
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(`research/260614-shard-spectrum-synthesis`, v3).
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### 6.1 The fifteen capability spectra
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Each binding declares a position on each axis. Core algorithms read these positions; there is
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no per-backend code in core (I-3).
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1. **Addressing granularity** — none → path → page-level store-id → in-file span → in-file
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block id (Logseq `id::`) → store-UUID → portable tumbler (Xanadu, the unreached ideal)
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2. **Content identity** — none → path/title → fingerprint → span-set
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3. **Identity vs placement** — path=identity → identity separated from placement (Trilium
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note/branch = a DAG)
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4. **Structure** — flat MD → frontmatter/`key::` → `%META%` → typed objects → DB schema+
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relations → object-graph/ontology → computed (inherited+templated) → typed-graph statements
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5. **History** — none → internal-only / CRDT-log → open-file → git-native
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6. **Merge model** — none → git/text → conflict-notes/keep-both → native-CRDT → coexist-with-rank
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7. **Native query** — none → text → build-your-own derived index → datalog/graph → DB query → SPARQL
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8. **Translation** — native → lossless → lossy-with-fidelity-report (incl. HTML)
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9. **Attachment mode** — file-store (native | interchange-mirror) → git-IS-store → in-engine-host
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→ local-REST → external-API → direct-DB → CRDT-replica → P2P/no-central-endpoint
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10. **Operational envelope** — local/unbounded → realtime CRDT/WebSocket → rate-limited/
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eventually-consistent/paginated
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11. **Access grant** — open → token → OAuth scoped+revocable → P2P key/invite → enterprise ACL
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12. **Content opacity** — plaintext → structured re-evaluable value → encrypted whole-shard →
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per-item → proprietary-lossy-exportable
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13. **Write granularity** — whole-file (TiddlyWiki) → per-page → section/anchor → per-block → story-item
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14. **Provenance granularity** — per-shard → per-page → per-edit → per-statement/value (Wikibase rank+refs)
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15. **Computational / liveness** — static source → captured-output snapshot → live-over-files →
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view-time render → irreducibly-live/temporal
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### 6.2 Operation verbs
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`read, write, diff, merge, lock, version, publish, notify, transclude-source,
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translate-syntax, structured-payload, derive-projection, execute/evaluate`. The last two are
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**gated, off by default** (§8, computational content). Verb support is part of the profile and
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must reconcile with the federation-ops capability matrix (SHARD-WP-0002 T10).
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### 6.3 Attachment-mode taxonomy (axis 9, expanded)
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A backend may offer **several** modes; attach mode is a **per-binding, capability-gated
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choice**, with one declared authoritative. Modes: file-store (native vault/folder *or* an
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interchange/sync mirror), **git-IS-store** (the home case — forge wikis & ikiwiki: git is the
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store *and* the journal at once, resolving the engine-mirror write-race), in-engine hosted
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adapter (XWiki component, Obsidian/Logseq/Roam plugin, Trilium script), local-REST (Joplin
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Data API, Trilium ETAPI), external-API-only (Notion), direct-DB (MojoMojo schema→model),
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CRDT-replica (Anytype/AFFiNE/AppFlowy), P2P/no-central-endpoint. **Boundary:** a monolithic
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live-memory blob (Smalltalk image, a kernel) is **never** an attach target — it participates
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only via export→files (I-12).
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### 6.4 Contract rules
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- **Versioned interface** (Foswiki::Store + Foswiki::Meta is the proof that a stable
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store-interface-with-swappable-backends works). Capability discovery is a static profile
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with optional runtime negotiation.
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- **Backend-swap tolerance** — shard identity/provenance survives a substrate change
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(RCS↔PlainFile, folder→Git, Logseq file→SQLite): bind to *capabilities*, not to "it's files."
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- **Absence is first-class** — the profile must express *can't* cleanly (Oddmuse floor), so
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degradation paths are explicit, never guessed.
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---
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## 7. Top waist — the Wiki Page Model (L2)
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Backend-neutral, **Markdown-first but stretchable many ways at once**. The page model is the
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lingua franca every consumer sees; an adapter's job is to project its backend into this model
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(read) and accept overlays back (write), within its capabilities.
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### 7.1 Page shapes the model must carry
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- **Prose Markdown** — the baseline.
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- **Typed / computed records** — frontmatter/`%META%`/XObjects/Notion DB rows; **computed
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metadata** (Trilium inherited+templated) represented as *effective-vs-own with per-attribute
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provenance*.
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- **Typed-graph statements** — Wikibase claim + qualifiers + references + rank (structure
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far-end).
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- **Inline-embedded objects** — Quip/Notion spreadsheets & live apps inside prose.
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- **Non-Markdown assets** — drawings, canvases, images: typed asset / opaque blob / pluggable
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content-type registry, never silent-flattened.
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- **The four computational shapes** (§8): one-source-many-projections, notebook (embedded
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computed output), program-as-page, live/temporal.
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All shapes reduce to a common skeleton: **`(content | source, structure, provenance envelope,
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[derivation rule])`**. The page model stores the richest faithful form as canonical and treats
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any Markdown rendering of a non-Markdown shape as a *lossy projection* (I-4 + fidelity report).
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### 7.2 Identity, placement, addressing — three distinct concepts
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The earlier draft used "identity" for two different things and (worse) suggested deriving page
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identity from a content fingerprint — which would make *editing a page change its identity* and
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break every reference to it (review bug B-1). They are pulled apart here:
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- **Page identity — a *stable handle*.** A shard-scoped, durable key that **survives edits**:
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the backend's native page/note id where one exists (Roam/Notion/Trilium uid, a git path
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treated as a name, a wiki page name), wrapped in a shard scope so it survives projection and
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never collides across shards. Identity is *assigned/minted, not computed from content*.
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References, placement, transclusion targets, and overlays all key on identity.
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- **Placement — *where* an identity sits.** One identity → N placements (paths/shards) = a DAG;
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no single canonical path (I-9). Placement can change without changing identity.
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- **Content equivalence — *detecting sameness*, never identity.** A **content fingerprint** (or
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span-set overlap) identifies a *version / a piece of content*, used to detect that two
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*distinct identities* hold the same or derived content (the equivalence/chorus mechanism,
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§8.4). A fingerprint is never a page's identity: same page, edited → new fingerprint, **same
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identity**; two pages, identical content → same fingerprint, **different identities**.
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- **Span addressing** — a sub-page address within an identity: adopt native span IDs where
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minted (Roam `:block/uid`, Logseq `id::`, Notion/CRDT UUID); else a *position* address
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(path+range) or a *content-fingerprint* address for equivalence/transclusion. The Xanadu
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tumbler is the portable ideal the scheme aims at without requiring.
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- **Provenance envelope** rides on pages and spans (see §7.3 for its layered, low-cost form).
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So the chain is: **identity (stable) → placements (N, mutable) → equivalence (cross-identity
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sameness, fingerprint-based)** — three concepts, three mechanisms, never conflated.
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---
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## 8. Coordination, federation & projection
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### 8.1 Coordination journal (L3) — Git as the spine
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Every information space has a Git-backed coordination journal (I-6). It records cross-shard
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operations (fork, import, reconcile, overlay-apply, space-branch) and **is** the history floor
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(I-10). For git-IS-store shards the shard's own git log *is* this journal; for non-git shards
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the journal supplements (begins-now / mirrors-forward / snapshots-replica) or imports
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(backfill open file history). History portability is a spectrum, handled per profile (axis 5).
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### 8.2 Overlay / patch engine (L3)
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The default write path for anything below write-through capability (I-5): an edit becomes a
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draft → patch/commit → MR, applied destructively only on explicit intent and only where the
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profile + policy both permit. This is what lets a read-only or rate-limited or lossy backend
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still be *edited* safely.
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### 8.3 Federation is plural & composable (L3) — the model taxonomy
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Federation is not one mechanism. shard-wiki selects a **federation model per space and
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composes per shard** (mechanism over policy, I-7):
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| Model | Anchor | Coordination shape |
|
||
|-------|--------|--------------------|
|
||
| **Fork + journal** (default home case) | Federated Wiki | copy-with-provenance + per-page action journal (story = replay) |
|
||
| **VCS-replication + ping** | ikiwiki | git clone/pull/push + change-ping |
|
||
| **Query-time graph-join** | Wikibase SPARQL `SERVICE` | join remote graphs at query time, no copy |
|
||
| **Feed aggregation** | RSS/Atom | inbound feed → pages |
|
||
| **Activity streams** | ActivityPub | Create/Update events, notify or content-bearing |
|
||
| **Engine-mirror** | Wiki.js DB↔Git | engine syncs its own store to a git mirror |
|
||
|
||
### 8.4 Union & projection (L4) — the derived cache
|
||
|
||
This whole layer is **derived-disposable**: recomputable from canonical state — sharded
|
||
content + the **coordination-canonical** inputs in the journal (I-2). Crucially, the *automatic*
|
||
equivalence results are derived, but the **human/curatorial inputs they consume — alias tables
|
||
and curator equivalence bindings — are coordination-canonical (they live in the journal), not
|
||
derived**; recompute reads them, never regenerates them. It comprises:
|
||
|
||
- **Identity resolution & equivalence** — detect "same topic / derived content" path-
|
||
independently from *derived* signals (content fingerprint, span-set overlap) **plus** the
|
||
*coordination-canonical* inputs (alias table, curator binding); present as
|
||
**chorus-of-voices** or designated-canonical (a *policy* preset). (Scaling: §8.7.)
|
||
- **Union graph** — the navigable join of pages, links, and dimensions (namespace, genealogy,
|
||
version, shard, equivalence). A *derived lens over canonical files+journal, never a new
|
||
store* (the ZigZag boundary).
|
||
- **Transclusion** — one **reference-not-copy** primitive unifying Xanadu transclusion, ZigZag
|
||
clone, Roam/Obsidian/Logseq embed, Notion synced block, Trilium note-cloning, and literate
|
||
named-chunk assembly, over the addressable union.
|
||
- **Projection — the two-axis model:**
|
||
- *Kind:* **replication-projection** (lazy cache of remote content — the default) vs
|
||
**derivation-projection** (transform/compile/weave/evaluate a source).
|
||
- *Liveness:* static → captured snapshot → live-over-files → view-time → irreducibly-live.
|
||
- Derivation facets: materialization timing (ahead-of-time vs view-time), multiplicity (one
|
||
output vs N co-equal), continuity (one-shot vs continuous). Every projection declares its
|
||
liveness + freshness + provenance; the irreducibly-live far end has no faithful static
|
||
form (source + a marked recording).
|
||
- **Moldable view registry** — projection generalises to an **open, type-keyed set of
|
||
co-equal, possibly-computed views, none canonical-by-fact** (display-canonical is policy).
|
||
This unifies replication/derivation/dimensional/query projection and answers the "pluggable
|
||
content-type registry" question (GT prior art).
|
||
- **Derived query index** — delegate to a shard's native query engine where present
|
||
(Roam/Logseq Datalog, Notion DB query, XWiki XWQL, Wikibase SPARQL); else build a derived
|
||
index over the projection (the Logseq DataScript-over-files pattern). The index is
|
||
disposable (I-2).
|
||
|
||
### 8.5 Computational / executable content — the scope decision
|
||
|
||
**In scope as a page-model + projection concern; out of scope as an execution platform.**
|
||
shard-wiki *recognises* computational types, attaches the **canonical source**, and presents
|
||
derived forms as **provenance- and liveness-marked projections**. Driving a derivation
|
||
(tangle/weave, re-execute a notebook, render a sketch, evaluate a pattern) is a **gated
|
||
capability, off by default, with a trust/sandbox concern, degrading to a captured snapshot**.
|
||
One snapshot-provenance record (run id, source rev, timestamp, environment "unguaranteed")
|
||
serves notebooks, renders, and recordings alike. **No INTENT amendment is required** — this
|
||
lives inside the existing page model (L2) and projection model (L4).
|
||
|
||
### 8.6 Consistency, concurrency & conflict model
|
||
|
||
INTENT makes real-time cross-shard consistency a non-goal — but "no strong consistency" is not
|
||
the same as "no defined consistency." This is the guarantee shard-wiki *does* offer, and the
|
||
mechanism (not policy) that makes concurrent editing safe (review bug B-2).
|
||
|
||
**The consistency guarantee — causal, anchored on the journal:**
|
||
|
||
- **Read-your-writes for coordination-canonical state.** Once an overlay/binding/merge is
|
||
committed to the journal, this client always sees it (the journal is the client's own causal
|
||
spine). This is a *strong* local guarantee, cheap because the journal is local Git.
|
||
- **Causal consistency across the derived tier.** The union/index/projections reflect a causal
|
||
cut of `(sharded inputs seen so far, journal)`. Effects never appear before their causes; a
|
||
projection that has seen journal commit *C* has seen everything *C* depends on.
|
||
- **Eventual convergence for sharded-canonical inputs.** Remote shard content is pulled
|
||
asynchronously (lazily or by notify/poll, §8.7); the union converges to each shard's latest
|
||
*as observed*, bounded by the shard's operational envelope. Freshness is always *shown*
|
||
(provenance envelope), never faked — a stale projection is labelled stale, not wrong.
|
||
|
||
So: **strong + read-your-writes for what shard-wiki owns (the journal); causal for what it
|
||
derives; eventual + freshness-labelled for what shards own.** No global clock, no distributed
|
||
transaction, no two-phase commit across shards — none is needed, because shard-wiki coordinates
|
||
rather than controls.
|
||
|
||
**Conflict detection & representation is core mechanism; only resolution is policy (I-7).**
|
||
The split the earlier draft elided:
|
||
|
||
- **Detection (core).** Divergence is detected structurally: two identities resolve as
|
||
equivalent (§8.4) but their content fingerprints differ, or an overlay's base revision no
|
||
longer matches the shard's current revision. Detection is always on; it is never optional.
|
||
- **Representation (core).** A detected conflict is **first-class data in the union**, not an
|
||
error: equivalent-but-divergent pages are presented as a **coexisting set** (the
|
||
chorus/keep-both representation), each fully attributed, with the divergence recorded in the
|
||
provenance envelope (union without erasure — a conflict is information, not a failure).
|
||
- **Resolution (policy).** *Which* version wins, or whether they stay coexisting, is a
|
||
configurable preset (§10): chorus / designated-canonical / git-merge / vote-to-merge /
|
||
overlay-only. Core never hard-codes one.
|
||
|
||
**Overlay-apply under source drift (the concurrent-write case).** An overlay carries the
|
||
**base revision** of the shard content it was authored against. On apply, core compares base to
|
||
the shard's current revision:
|
||
|
||
- *unchanged* → apply (fast-forward), commit to journal, propagate if the profile permits;
|
||
- *changed, non-overlapping* → three-way merge where the merge capability allows (axis 6),
|
||
else keep-both;
|
||
- *changed, overlapping* → **refuse + re-present** as a conflict (above); never silently
|
||
clobber (I-5, no silent remote mutation). The unapplied overlay remains coordination-
|
||
canonical and valid against its base.
|
||
|
||
**Ordering.** The journal commit is the ordering authority for coordination-canonical effects;
|
||
a shard-native write is only *acknowledged* in the journal after the adapter confirms it, so a
|
||
crash between journal-intent and shard-write is recoverable (the intent is replayable, the
|
||
write is idempotent-keyed on identity+base-rev). Cross-shard operations are ordered by their
|
||
journal commits, giving the causal cut above.
|
||
|
||
**Residual open items** (tracked in *Known scaling risks & open problems*, §12, not pretended
|
||
solved): the exact convergence bound for
|
||
high-write CRDT shards under partition, and whether per-equivalence-set divergence needs a
|
||
vector clock vs. a simple base-rev comparison, are deferred to implementation spikes.
|
||
|
||
---
|
||
|
||
## 9. Cross-cut — Authorization (L5)
|
||
|
||
Fully specified in **`ArchitectureBlueprint.md`** (the access & history sub-blueprint);
|
||
summarised here for completeness:
|
||
|
||
- **One core, a ladder of modes** L0 (open/c2, zero deps) → L1 (attributed) → L2
|
||
(authenticated) → L3 (role/group) → L4 (multi-tenant enterprise). Climbing is configuration,
|
||
not re-architecture.
|
||
- **PEP** wraps every adapter op; **PDP** decides `(principal, action, target)` over actions
|
||
`read/write/patch/merge/administer`, layered on the adapter's capability profile (a shard
|
||
that can't write can't be written regardless of policy — L5 consults the L1 rail).
|
||
- **Authentication delegated** to a pluggable IdentityProvider (null provider = L0 default);
|
||
real identity from `user-engine` over `net-kingdom` IAM.
|
||
- **Fail open only at L0, fail closed at L2+.** Authorization is pure/offline once a Principal
|
||
is resolved. Provenance carries authz context so the union never leaks unreadable content
|
||
(the L5↔provenance-rail interaction).
|
||
|
||
---
|
||
|
||
## 10. The policy surface (mechanism over policy, made concrete)
|
||
|
||
I-7 only means something if the policy knobs are enumerated and kept *out* of core algorithms.
|
||
The configurable presets are:
|
||
|
||
- **Canonical-source policy** — chorus / designated-canonical / git-merge / overlay-only /
|
||
vote-to-merge (per space or per equivalence set).
|
||
- **Federation model** — the §8.3 taxonomy, per space, composable per shard.
|
||
- **Shard mode** — read-only / write-through / mirrored / projected / cached / canonical
|
||
(constrained by the capability profile).
|
||
- **Reconciliation cadence & conflict exposure** — push/poll/manual; show-conflicts vs
|
||
auto-merge-when-supported.
|
||
- **Execution policy** — derive/execute off (default) / sandboxed / per-shard-allowed.
|
||
- **Authorization mode** — the L0–L4 ladder.
|
||
- **Projection materialization** — lazy/eager; snapshot vs view-time; recording retention.
|
||
|
||
Core ships sane defaults (L0 open; fork+journal; lazy replication-projection; overlay-before-
|
||
mutation; execution off) and never hard-codes any of the above.
|
||
|
||
---
|
||
|
||
## 11. Concrete module structure (bridge to implementation)
|
||
|
||
A proposed package layout for `src/shard_wiki/`, mapping 1:1 to the layers so the dependency
|
||
rule (downward only; L4 rebuildable) is enforceable by import lint:
|
||
|
||
```
|
||
src/shard_wiki/
|
||
model/ # L2 top waist: Page, Identity, Placement, ProvenanceEnvelope,
|
||
# Span, the page-shape types; capability-spectrum value types
|
||
adapters/ # L1 bottom waist: AdapterContract (versioned iface), CapabilityProfile,
|
||
# attachment-mode binding; concrete adapters:
|
||
git/ folder/ gitea/ obsidian/ webdav/ notion/ … # each: profile + verbs
|
||
coordination/ # L3: GitJournal, OverlayEngine (draft→patch→MR), reconcile
|
||
federation/ # L3: FederationModel strategies (fork_journal, vcs_ping,
|
||
# graph_join, feed, activitypub, engine_mirror)
|
||
union/ # L4 (derived): IdentityResolver, EquivalenceGraph, UnionGraph,
|
||
# Transclusion (reference-not-copy)
|
||
projection/ # L4 (derived): ReplicationProjection, DerivationProjection,
|
||
# ViewRegistry (moldable), QueryIndex (delegate|derive)
|
||
authz/ # L5 cross-cut: PDP, PEP, IdentityProvider iface, NullProvider
|
||
provenance/ # cross-cut: the envelope plumbing used by every layer
|
||
api/ # L6: orchestrator API (server-side union for agents/CLI)
|
||
```
|
||
|
||
Hard import rules: `union/` and `projection/` may import `model/`, `adapters/`,
|
||
`coordination/` but **nothing may import them** (they are the disposable middle). `model/` and
|
||
`adapters/` import nothing else in the tree except `provenance/` (the waists stay thin).
|
||
|
||
---
|
||
|
||
## 12. Canonical data flows (the architecture exercised)
|
||
|
||
**A. Attach a shard.** Adapter binds (chosen attachment mode) → probes/declares a capability
|
||
profile → core registers the shard under a root entity → if not git-native, the coordination
|
||
journal is seeded (begin-now/mirror/import per axis 5). No union rebuild yet (lazy).
|
||
|
||
**B. Read a page through the union.** Consumer asks the union for an identity → Identity
|
||
resolver maps it to placements across shards → equivalence yields chorus or canonical →
|
||
replication-projection lazily fetches from each shard (cache + freshness) → page returned
|
||
wrapped in its provenance envelope → L5 filters anything the principal can't see at source.
|
||
|
||
**C. Edit a read-only / limited shard.** Write request → L5 PDP allows → capability profile
|
||
says < write-through → OverlayEngine records a draft → renders a patch/MR in the shard's native
|
||
syntax (lossless) or Markdown (lossy-with-report) → on explicit apply, commit to the journal
|
||
and (if the profile permits) propagate; otherwise the overlay stands as the local truth, fully
|
||
attributed.
|
||
|
||
**D. Attach a computational notebook.** Adapter declares profile (attachment=file-store,
|
||
opacity=mixed, computational=captured-output). Core attaches the `.ipynb` **source** as
|
||
canonical; presents cells + embedded outputs as **derivation-projection snapshots** marked
|
||
"run N, env unguaranteed"; offers a static render via the view registry; re-execution stays
|
||
gated off. History uses paired-text/nbdime per axis 5.
|
||
|
||
---
|
||
|
||
## 13. Key tradeoffs & decisions to confirm
|
||
|
||
Resolved here:
|
||
|
||
- **Capability spectra over a verb checklist** — accept richer contract complexity for precise,
|
||
uniform degradation. (Decided: spectra.)
|
||
- **Derived middle is a cache, not a store** — accept recompute cost for rebuildability,
|
||
provenance, and graceful degradation. (Decided: cache.)
|
||
- **Default federation = fork+journal over Git** — the home case; other models opt-in. (Decided.)
|
||
- **Execution off by default** — recognise+project always; execute only when gated on. (Decided.)
|
||
|
||
Open — to confirm before SHARD-WP-0002 spec-writing finalises:
|
||
|
||
1. **Union graph persistence.** Pure-recompute (simplest, honours I-2 hardest) vs a persisted-
|
||
but-disposable cache (faster, must guarantee rebuild equivalence). *Recommendation:
|
||
persisted-but-disposable with a `rebuild` that must reproduce it byte-for-byte.*
|
||
2. **Address scheme.** Ship shard-scoped native-id wrapping now and treat a portable tumbler as
|
||
a later capability, or design the tumbler up front? *Recommendation: wrap native ids now.*
|
||
3. **L1 "attributed-but-open" mode** — ship it or jump L0→L2? (Carried from ArchitectureBlueprint.)
|
||
4. **Per-page ACL default** — off (per-shard/namespace) confirmed; revisit only if demand appears.
|
||
|
||
---
|
||
|
||
## 14. What this architecture is *not*
|
||
|
||
- Not a wiki engine, UI, or rendering pipeline (those are consumers at L6).
|
||
- Not a canonical-source-of-truth — shards keep sovereignty; the middle is derived.
|
||
- Not a generic file-sync daemon — synchronisation is wiki-page-semantic.
|
||
- Not an execution platform — computation is recognised and projected, not hosted.
|
||
- Not a universal ontology — no single schema is imposed on all shards.
|
||
- Not an authentication/identity store — that is delegated (authorization is owned).
|
||
|
||
---
|
||
|
||
## 15. Traceability
|
||
|
||
- **INTENT** — every invariant in §2 cites an INTENT principle or boundary; no invariant
|
||
contradicts the Stability Note.
|
||
- **Research** — §6 (spectra) ← `260614-shard-spectrum-synthesis` v3; §8.3 (federation
|
||
taxonomy) ← v3 §2.5; §8.4–§8.5 (two-axis projection, view registry, computational scope) ←
|
||
`260614-computational-page-model-synthesis`; §7 page shapes ← the engine + modern-tool +
|
||
computational dives; §1 thesis ← the files-canonical/index-derived through-line across
|
||
Logseq/ikiwiki/GT/Pharo/Jupyter.
|
||
- **Use cases** — the architecture is sized to UC-01–UC-84: federation/coordination (UC-01–07,
|
||
26–33, 56, 71–72, 79) → §8; attachment/adapter (UC-34–43, 50, 53, 57, 60–62, 64–66, 68–70,
|
||
76–82) → §6; page model & fidelity (UC-34, 39, 42, 55, 58–59, 67, 73, 80, 83–84) → §7/§8.5;
|
||
addressing/identity/query (UC-32, 44–49, 51–52, 54, 63, 74) → §7.2/§8.4; provenance &
|
||
metadata (UC-24–25, 75) → the provenance rail; collaboration & discovery (UC-08–23) → L6
|
||
consumers over the union.
|
||
- **Workplans** — §6–§8 are the design target of `SHARD-WP-0002` (T11–T18); §9 is owned by
|
||
`ArchitectureBlueprint.md`; §1 (yawex-derived resolution/overlay) aligns with
|
||
`SHARD-WP-0001`.
|
||
|
||
---
|
||
|
||
## 16. Stability note
|
||
|
||
This document defines shard-wiki's **internal** architecture; it may evolve as the spec
|
||
workplans land. But the **thesis (§1)**, the **invariants (§2)**, and the **dual narrow waist
|
||
(§1, §6, §7)** are load-bearing — changing any of them is an architectural change in the sense
|
||
of INTENT's Stability Note and should be rare and deliberate.
|