tegwick
60e1aa661c
Xanadu studied as conceptual ancestor, not a candidate shard. Yield: reference-not-copy EDL/xanadoc validates projection+overlay+union; content-identity bidirectional transclusion; portable span-address (tumbler) problem logged as adapter-contract architecture for SHARD-WP-0002. Recorded design-bug boundaries: reject single-global-docuverse, single-canonical-instance, baked-in economic policy. Added UC-44/45/46; enriched UC-24/27/29/32. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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260614 — Project Xanadu deep dive (the docuverse, the EDL, reference-not-copy)
Date: 2026-06-14
What this is
A focused study of Project Xanadu (Ted Nelson) read through shard-wiki's lens.
Unlike the engine dives (xwiki, twiki, foswiki), Xanadu is not a candidate
shard backend — it never shipped at scale and there is nothing to attach. It is
studied as the deepest conceptual ancestor of shard-wiki's own model: several
shard-wiki primitives turn out to be Xanadu mechanisms under different names.
The distinctive material:
- the EDL / xanadoc — a document that contains no content, only an ordered list of spans (content references) plus xanalinks (separate link tables); the client assembles the page by reference → this is shard-wiki projection + union
- the storage substrate — tumblers (stable fine-grained addresses), istream (invariant content pool), enfilades / spanfilade (virtual↔content mapping, version comparison by span-set intersection)
- content-identity, bidirectional transclusion — content "knowably in more than one place" that remembers all its appearances → stronger than UC-32
- transcopyright / micropayment — a baked-in rights policy shard-wiki must keep configurable, not inherit
Goes deliberately underneath the surface pattern table in
research/260608-federation-concepts/findings.md §3.3, which it extends rather than
repeats.
Contents
| Path | Role |
|---|---|
findings.md |
EDL/xanadoc, addressing substrate, transclusion, versioning, rights, INTENT mapping (reinforcements + design-bug divergences), UC seeds, architecture notes, sources |
Status
Initial deep dive complete. Three new use cases promoted to spec/UseCaseCatalog.md
(UC-44 compose-by-reference, UC-45 reverse transclusion, UC-46 content-identity
equivalence); UC-24/27/29/32 enriched. Span-addressing as an adapter capability,
content identity, composition manifests, and reuse-terms metadata logged as
architecture for workplans/SHARD-WP-0002-federation-architecture.md.
Key boundary recorded: shard-wiki inherits Xanadu's reference-not-copy mechanisms but rejects the single-global-docuverse premise, the single-canonical-instance model, and the baked-in economic policy — those would violate shard sovereignty, parallel-version support (UC-27), and mechanism-over-policy.