# Synthesis — the shard spectrum: one capability model across the full dive set

Date: 2026-06-14 · **revised 2026-06-14 (v2)** — extended from nine systems to the full
set (added Joplin, Logseq, the CRDT local-first cohort — Anytype/AFFiNE/AppFlowy — and
Trilium); spectra grown from eleven to **thirteen**.
Source kind: **synthesis** — consolidates every deep dive into a single comparative model
feeding the **shard adapter contract** (`SHARD-WP-0002` T11–T16)
Lens: shard-wiki — what a backend must expose to participate, expressed as *spectra* of
capability rather than a yes/no checklist

> Purpose. Fourteen tools/systems have now been studied (plus the wiki-engines
> landscape): two conceptual ancestors (**Xanadu, ZigZag**); four engines (**XWiki,
> TWiki, Foswiki** + landscape); and the modern note/PKB tools (**Roam, Obsidian,
> Notion, Joplin, Logseq, Anytype, AFFiNE, AppFlowy, Trilium**), against the federation
> and origin research. This document reads them *across* each other. The payoff is a
> small set of **capability spectra** — now **thirteen** — each anchored at both ends by
> a real system, with federation operations degrading by position. That spectrum *is*
> the adapter contract's design surface. v2 folds the post-engine use cases (**UC-44–
> UC-67**) into the `SHARD-WP-0002` tasks.

Inputs: `research/260608-{federation-concepts,wikiengines-overview,c2-wiki-origins,yawex-prior-art}`,
`research/260613-{xwiki,twiki,foswiki}-deep-dive`,
`research/260614-{xanadu,zigzag,roam,obsidian,notion,joplin,logseq,localfirst-workspaces,trilium}-deep-dive`.
Output target: `spec/TechnicalSpecificationDocument.md` (adapter contract) via
`SHARD-WP-0002`.

---

## 1. The shard family matrix

Candidate-shard backends across the dimensions that matter to the contract. (Xanadu and
ZigZag are *not* shards — they are the conceptual ideals each column aspires to; listed
last as reference anchors.)

| Backend | Substrate | Attach mode(s) | Addressing | Structure | History | Merge | Query | →Markdown | Opacity |
|---------|-----------|----------------|-----------|-----------|---------|-------|-------|-----------|---------|
| **Git folder / repo** | files | file-store | path (+ commit) | flat MD + frontmatter | **git-native** | git/text | no | native | none |
| **Obsidian** | files | file-store **/** plugin | path + in-file `^id` | frontmatter (in-file) | none (Git plugin) | git/text | plugin (Dataview) | native (OFM) | none |
| **Logseq** | files (MD/Org) → SQLite (DB-graph) | file-store **/** plugin | **in-file block `id::`** (sweet spot) | `key::` props (in-file) | none (git) | git/text | **Datalog (derived)** | native-ish | none |
| **TWiki / Foswiki** | files + RCS / pluggable | file-store **/** API | path | `%META%` in-file (N records) | **open file (RCS/PlainFile)** | git/text | no | lossless (TML) | none |
| **Trilium** | SQLite (one file) | **ETAPI** / scripting / DB | `noteId` + **`branchId`** (id≠place) | labels+relations, **inherited+templated**; **DAG** | internal revisions | conflict-res | attr search | **lossy (HTML)** | **per-note** |
| **Joplin** | SQLite-local | **sync-mirror** / local-REST / plugin | page-level `:/id` (store) | notebooks + tags | internal revisions | conflict-notes | search | lossy | E2EE (whole) |
| **XWiki** | DB (Hibernate) | in-engine host / REST | path | **XObjects/XClass** | internal (`xwikircs`) | git/text | yes (XWQL) | engine syntax | none |
| **Roam** | client DataScript | **in-app host only** | **store UUID** | `key::` attrs | internal (txn log) | (in-app) | yes (Datalog) | (Roam MD) | none |
| **Notion** | hosted Postgres | **external API only** | store UUID | **DB schema + relations + rollups** | internal, not portable | internal | yes (DB query) | **lossy** | none |
| **Anytype** | **CRDT (any-sync)** | **replica / P2P node** | object id (store) | **typed object graph (ontology)** | CRDT log | **native-CRDT** | graph | lossy | **E2EE (whole)** |
| **AFFiNE** | **CRDT (Yjs)** | replica / self-host | block id (store) | blocks; **one-data-many-views** | CRDT log | **native-CRDT** | DB filters | lossy | optional |
| **AppFlowy** | **CRDT (Yrs)** | replica / self-host | block id (store) | **Notion-style DB + views** | CRDT log | **native-CRDT** | DB query | lossy | self-host |
| **TiddlyWiki** | single file | file-store | path | typed tiddlers | none | git/text | no | varies | none |
| **MediaWiki / Confluence** | DB | API | path | wikitext / macros | internal-only | internal | limited | lossy | none |
| — *Xanadu (ideal)* | permascroll | — | **tumbler (span)** | spans + links | permanent | content-merge | — | — | — |
| — *ZigZag (ideal)* | cells/dims | — | cell id | **N dimensions** | — | — | dimension walk | — | — |

Reading top to bottom is roughly shard-wiki's difficulty gradient: **Git/Obsidian/
Logseq** are friction-free file-store cases (Logseq adding block addressing on files);
**TWiki/Foswiki/Trilium** add translation and (Trilium) a DAG + computed metadata;
**XWiki/Roam/Notion** add DB structure and store addressing; the **CRDT cohort
(Anytype/AFFiNE/AppFlowy)** adds a new merge model and (Anytype) P2P+E2EE; **Notion** is
the hardest hosted case. Xanadu/ZigZag mark the ideals.

---

## 2. The capability spectra (the contract's real shape) — thirteen

Each capability is **not boolean** — it is a position on a spectrum anchored at each end
by a real system. The contract should model *positions*; federation ops degrade by
position.

1. **Addressing granularity** — `none → whole-page(path) → page-level store id(Joplin
   :/id, Trilium noteId) → in-file span(Obsidian ^id) → in-file block(Logseq id::, the
   sweet spot: block-level AND git-diffable) → store-minted span(Roam/Notion/CRDT UUID) →
   portable tumbler(Xanadu ideal)`. (UC-51, UC-44/45.)
2. **Content identity** — `none → path/title → fingerprint(hash) → span-set/equivalence
   (Xanadu)`. Drives equivalence + reverse-transclusion. (UC-46, UC-27.)
3. **Identity vs placement** *(new emphasis)* — `path = identity(most) → identity
   separated from placement(Trilium note/branch; a page in many locations = a DAG)`. The
   clean model for a page under multiple paths/shards. (UC-66, UC-22.)
4. **Structure** — `flat Markdown → in-file frontmatter/key::(Obsidian/Logseq) → in-file
   %META%(TWiki) → typed objects(XWiki) → DB schema+relations+rollups(Notion/AppFlowy) →
   typed object graph/ontology(Anytype) → computed: inherited+templated(Trilium)`.
   In-text federates; DB-locked needs sidecar+fidelity; **computed** needs effective-vs-
   own provenance. (UC-34, UC-39, UC-58, UC-67.)
5. **History** — `none → internal-only/not-portable(Notion/Joplin/Trilium) → CRDT update
   log(Anytype/AFFiNE/AppFlowy) → open file format(TWiki RCS) → git-native(Git/Obsidian/
   Logseq)`. Internal/CRDT-log ⇒ *supplement*; open-file ⇒ *import*; git ⇒ *adopt*.
   (UC-36, UC-41.)
6. **Merge model** *(new, 13th)* — `none → git/text merge → conflict-notes/keep-both
   (Joplin) → native-CRDT conflict-free(Anytype/AFFiNE/AppFlowy)`. A CRDT shard merges
   itself — **never impose git/text merge**; speak the CRDT (replica) or stay projection/
   overlay. (UC-64.)
7. **Native query** — `none → text search → build-your-own derived index(Logseq DataScript
   over files; shard-wiki can do likewise) → datalog/graph(Roam/Anytype) → DB query
   (Notion/AppFlowy/XWiki)`. Delegate where present; **build an index over the projection**
   where not. (UC-52, UC-63, UC-05, UC-54.)
8. **Translation to Markdown** — `native → lossless round-trip(Foswiki TML↔HTML) → lossy-
   with-fidelity-report(HTML/CKEditor Trilium; Notion blocks; CRDT/object models)`.
   Lossless ⇒ writable; lossy ⇒ read/projection floor + visible fidelity loss. (UC-42,
   UC-59, UC-03.)
9. **Attachment mode** *(expanded)* — a **per-binding, capability-gated** choice; a
   backend may offer several:
   - **file-store** — *native on-disk store*(Obsidian/Logseq/TWiki) **or** *interchange/
     sync mirror*(Joplin items on WebDAV/S3) (UC-40, UC-53, UC-60, UC-62)
   - **in-engine host** — adapter inside the app via its API (Roam/Obsidian/Logseq/
     Trilium scripting, XWiki components) (UC-38, UC-50)
   - **local-REST** — localhost API, app-running (Joplin Data API; Trilium ETAPI) (UC-38)
   - **external-API** — remote REST from outside (Notion) (UC-57)
   - **CRDT replica** — hold a local CRDT replica (Anytype/AFFiNE/AppFlowy) (UC-64)
   - **P2P / no-central-endpoint** — replica or peer/node, not a URL (Anytype) (UC-65)
10. **Operational envelope** — `local/unbounded → realtime CRDT/WebSocket → rate-limited+
    eventually-consistent+paginated(Notion ~3 rps)`. Sets live vs cache/poll/webhook.
    (UC-57, UC-31.)
11. **Access grant** — `open(L0) → token → OAuth scoped+revocable(Notion) → P2P key/invite
    (Anytype)`. The backend may *enforce* no-silent-mutation. (UC-57, UC-65,
    [[shard-wiki-auth-in-core-decision]].)
12. **Content opacity** *(new, 12th)* — `plaintext → encrypted-at-rest whole-shard(Joplin/
    Anytype E2EE) → per-item(Trilium protected notes — encrypted and plaintext coexist)`.
    Opaque content ⇒ backup/structure-shell only; never present ciphertext as readable.
    (UC-61.)
13. **Write granularity** — `whole-file(TiddlyWiki) → per-page/note(Git/Obsidian/Joplin/
    Trilium) → per-block(Roam/Notion/Logseq/CRDT)`. Sets overlay/patch/lock/conflict
    scope. (UC-35.)

*(Content types — Markdown-only → typed records → non-Markdown assets (Excalidraw/Canvas/
whiteboards/objects) — remains a cross-cutting page-model demand, tracked under structure
+ T12 rather than as a standalone capability. UC-55.)*

Design consequence: **T11's capability vocabulary = these thirteen spectra**, not a flat
`read/write/diff/...` list. The flat verbs remain the *operations*; the spectra are the
*profile* saying how well each verb is supported and how it degrades.

---

## 3. Cross-cutting findings (the through-lines)

- **Files-canonical, index-derived is the winning architecture.** Obsidian's
  MetadataCache, **Logseq's DataScript-over-files**, Git's working tree, and shard-wiki's
  projection model agree: the graph/backlinks/structured index are **derived and
  rebuildable**, never a second source of truth. Roam/Notion/CRDT invert this (store
  canonical) and pay in portability. shard-wiki keeps files+journal canonical.
- **Fine-grained addressing is real, adoptable, and can be git-diffable.** Roam/Notion/
  CRDT mint store UUIDs; Obsidian uses in-file `^id`; **Logseq resolves the tension —
  block-level `id::` that is also git-diffable text**. Adopt native IDs where present,
  fingerprint where not; portable span address stays the open ideal (Xanadu).
- **Identity ≠ placement.** *(new)* Trilium's **note vs branch** (a note cloned into many
  locations = a DAG) is the clean model for a page under multiple paths or across shards —
  separate *what a page is* from *where it sits*. The namespace-level form of the clone/
  reference primitive.
- **Transclusion ⇄ clone ⇄ embed ⇄ cloned-note is one primitive.** Xanadu transclusion,
  ZigZag clone, Roam/Logseq embed, Obsidian `![[ ]]`, Notion synced block, **Trilium note
  cloning** — one "reference-not-copy" primitive over an addressable union (UC-32/44/45/
  51/66).
- **CRDT changes the merge math.** *(new)* The CRDT cohort merges concurrent edits itself;
  shard-wiki must **not impose git/text merge** — speak the CRDT (replica) or stay a
  projection/overlay. A new **merge-model** capability (spectrum 6).
- **Structure & history federate iff in text; metadata can be computed.** `%META%`/
  frontmatter/`key::` diff and travel; XObjects/Notion-DB/CRDT lock in. *(new)* Trilium
  adds **computed metadata** (inherited+templated) — represent effective-vs-own, don't
  flatten.
- **Content opacity is per-item, not only whole-shard.** *(new)* Joplin/Anytype encrypt
  whole-shard; **Trilium encrypts per-note** — the opacity capability must be granular.
- **The attach surface is not always the native store.** *(new)* Joplin's best surface is
  its **sync mirror** (not its SQLite); Logseq offers file-graph **or** DB-graph, and is
  **migrating substrate** (file→SQLite). Bind to capabilities, not to "it's files."
- **The page model must stretch many ways at once:** prose Markdown, typed/computed
  records (N-per-page, relations, inheritance), non-Markdown assets, reference/query-
  defined pages, and **multi-placement (DAG) identity**. The heaviest demand on T12.

---

## 4. How the post-engine use cases fold into the workplan

UC-44–UC-67 (from the 260614 dives) map onto the adapter-contract tasks:

| UCs | Theme | Lands in |
|-----|-------|----------|
| UC-35, UC-50, UC-53, UC-57, **UC-60, UC-62, UC-64, UC-65** | attachment modes (file-store native/mirror, in-engine, local-REST, external-API, CRDT-replica, P2P) + operational envelope + merge model | **T11** + **T14** |
| UC-34, UC-39, UC-55, UC-58, **UC-67** | structured/typed/**computed** payload, non-MD assets, DB schema+relations | **T12** |
| UC-36 | internal/CRDT-log history = supplement | **T13** |
| UC-42, UC-59 | translation: lossless vs lossy-with-fidelity-report (HTML/blocks/CRDT) | **T15** |
| UC-31 | webhooks / realtime / push-vs-poll | **T6** / **T11** envelope |
| UC-57 §6, **UC-61, UC-65** | scoped grant; **content opacity** (whole/ per-item); P2P key | **T11** (access-grant + opacity) |
| UC-44, UC-45, UC-46, UC-51, **UC-63, UC-66** | span addressing, content identity, **identity≠placement**, transclusion-as-reference, derived index | **T16** (+ T12) |
| UC-47, UC-48, UC-52, UC-54 | dimensional navigation, query delegation/build, query-defined pages | **T16** (+ T5/T10) |

No new task needed — **T16** already owns the addressing/identity/navigation thread; v2
adds **identity≠placement (UC-66)** and **build-your-own derived index (UC-63)** to it,
and **computed metadata (UC-67)** + **non-MD/multi-placement** to **T12**.

---

## 5. Recommendations (decisions to record under SHARD-WP-0002)

1. **Model capabilities as the thirteen spectra (§2)**, not flat verbs. (T11.)
2. **Two new spectra: content opacity (per-item) and merge model.** A CRDT shard's merge
   is native — never git-merge it; an encrypted shard degrades to structure-shell. (T11.)
3. **Adopt native span IDs (prefer in-file/git-diffable, à la Logseq `id::`); fingerprint
   otherwise; keep portable-span-address open.** (T16/T11, UC-51/46.)
4. **Separate page identity from placement** (Trilium note/branch) in the page/namespace
   model — a page is one entity with N placements (paths/shards). (T12/T16, UC-66.)
5. **One reference-not-copy primitive** for transclusion/clone/embed/cloned-note over the
   addressable union. (T16, UC-32/44/45/66.)
6. **Prefer in-text structure; tolerate DB structure via sidecar+fidelity; represent
   computed (inherited/templated) metadata as effective-vs-own.** (T12/T15, UC-34/58/67.)
7. **Attachment mode is a per-binding, capability-gated choice** across the full set:
   file-store (native *or* interchange-mirror), in-engine-host, local-REST, external-API,
   CRDT-replica, P2P/no-central-endpoint. Bind to capabilities — substrate can migrate
   (Logseq). (T14, UC-40/38/50/57/60/62/64/65 + UC-43.)
8. **Query: delegate to a native engine where present; build a derived index over the
   projection where not** (Logseq pattern). (T16/T5, UC-52/63/54.)
9. **Keep files + coordination journal canonical; all indexes/projections derived and
   rebuildable.** (Architecture invariant, INTENT.)

These honor INTENT: mechanism over policy (spectra not hard-coded behaviors), union
without erasure (fidelity + effective-vs-own + identity/placement all preserve
information), graceful degradation (every capability has a read/projection floor; opaque/
CRDT shards degrade to backup/projection), no silent mutation (access-grant + opacity +
overlay + respect native merge), shard sovereignty (no backend forced to change
substrate; substrate may migrate), Markdown-first/backend-neutral (in-text preferred, DB/
CRDT/HTML tolerated).

---

## 6. Open questions escalated by the synthesis

1. **Portable span address** across heterogeneous backends — wrap native IDs (Roam/Notion/
   CRDT UUID, Logseq `id::`, Trilium noteId) in a shard-scoped address? (T16.)
2. **CRDT shards** — embed a CRDT client (Yjs/Yrs) for a live replica, or consume
   snapshots? Overlays as CRDT ops or out-of-band patches? (T14, UC-64.)
3. **Identity vs placement** — does shard-wiki adopt the note/branch split as its own page
   model, and is a cloned page one page with N placements or a transclusion? (T12/T16,
   UC-66.)
4. **Computed metadata** — materialize effective attributes (snapshot) or compute live
   from the shard's tree/templates, with per-attribute provenance? (T12, UC-67.)
5. **Page model breadth** — can one model carry prose + typed/computed records + non-MD
   assets + query-defined pages + multi-placement identity coherently? (T12.)
6. **External-API write-through at scale** (Notion ~3 rps) vs read/projection default.
   (T14, UC-57.)
7. **Content opacity** — what is visible for an opaque shard/item (IDs/structure vs
   nothing); does shard-wiki ever hold keys? (T11, UC-61.)

---

## 7. Sources

A synthesis; primary sources are the fourteen dives' `findings.md` files plus
`research/260608-{federation-concepts,wikiengines-overview,c2-wiki-origins,yawex-prior-art}`.
No new external research was performed in v2.

Cross-references: `spec/UseCaseCatalog.md` (UC-26–UC-67),
`workplans/SHARD-WP-0002-federation-architecture.md` (T1–T16),
`INTENT.md` (constraints), [[shard-wiki-auth-in-core-decision]].

---

## 8. Traceability

- Consolidates: all fourteen deep dives + federation/origin research into one capability
  model (v2).
- Feeds: `SHARD-WP-0002` T11 (**thirteen-spectra** vocabulary, incl. content-opacity +
  merge-model), T12 (page-model breadth: computed metadata, identity≠placement, non-MD),
  T13 (history incl. CRDT-log = supplement), T14 (full attachment-mode taxonomy incl.
  CRDT-replica + P2P + interchange-mirror + local-REST), T15 (lossy incl. HTML), T16
  (addressing, content identity, identity≠placement, derived index, dimensional/query).
- UC coverage extended in the workplan from UC-34–UC-59 to **UC-34–UC-67**.
- No UCs added (synthesis only); no boundary changes (INTENT Stability Note untouched).
</content>