shard-wiki/research/260614-shard-spectrum-synthesis/README.md

# 260614 — Shard spectrum synthesis (one capability model across the full dive set)

Date: 2026-06-14 · **revised 2026-06-14 (v2)**

## What this is

A **synthesis** (no new external research) that reads every studied system *across* the
others and distills them into a single comparative model feeding the **shard adapter
contract** (`SHARD-WP-0002`).

**v2** extends from nine systems to the full set and grows the spectra from eleven to
**thirteen**. The systems: two conceptual ancestors (**Xanadu, ZigZag**), four engines
(**XWiki, TWiki, Foswiki** + the wiki-engines landscape), and the modern note/PKB tools
(**Roam, Obsidian, Notion, Joplin, Logseq, Anytype, AFFiNE, AppFlowy, Trilium**), against
the federation/origin research.

Centerpieces:
- **The shard family matrix** — every candidate backend × {substrate, attach mode(s),
  addressing, structure, history, **merge**, query, →Markdown, **opacity**}, with Xanadu/
  ZigZag as the ideal anchors.
- **The thirteen capability spectra** — the claim that the adapter contract should model
  *positions on spectra*, each anchored at both ends by a real system, with federation
  ops degrading by position. v2 adds **content opacity** (12th) and **merge model**
  (13th), plus emphasis on **identity vs placement**, and expands the attachment-mode
  spectrum (file-store native/interchange-mirror, in-engine-host, local-REST,
  external-API, CRDT-replica, P2P/no-central-endpoint).
- **UC-44–UC-67 → workplan task mapping** (T11–T16).

## Contents

| Path | Role |
|------|------|
| `findings.md` | Family matrix, the thirteen spectra, cross-cutting through-lines, UC→task fold-in, recommendations/decisions, escalated open questions |

## Status

Synthesis v2 complete. No new use cases (consolidation only). Feeds `SHARD-WP-0002`: T11
reframed around the **thirteen spectra** (incl. content-opacity + merge-model); T12
page-model breadth (prose + typed/**computed** records + non-Markdown assets +
query-defined + **multi-placement/DAG identity**); T13 history (incl. CRDT-log =
supplement); T14 **full attachment-mode taxonomy** (CRDT-replica + P2P + interchange-mirror
+ local-REST added); T15 lossy-with-fidelity-report (incl. HTML); T16 (addressing, content
identity, **identity≠placement**, derived index, dimensional/query). UC coverage extended
UC-34–UC-59 → **UC-34–UC-67**.

**New through-lines (v2):** CRDT changes the merge math (native merge — never impose git
merge); identity ≠ placement (Trilium note/branch) is the model for multi-location/
multi-shard pages; metadata can be computed (inherited/templated), not just stored;
content opacity is per-item, not only whole-shard; the attach surface is not always the
native store (Joplin sync mirror; Logseq file-vs-DB and its substrate migration); the
block-graph-on-files sweet spot (Logseq `id::`) resolves the addressing tension.
**Carried from v1:** files-canonical/index-derived; fine-grained addressing is adoptable;
transclusion=clone=embed is one primitive; structure/history federate iff in-text; attach
mode is per-binding; Notion proves the platform can enforce no-silent-mutation.
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