# 260613 — Foswiki deep dive (store abstraction, extension API, ecosystem)

Date: 2026-06-13

## What this is

A focused study of **Foswiki** — the community fork of TWiki (2008, from TWiki
4.2.x) — concentrating on **what Foswiki changed**, not the lineage it shares with
TWiki. The distinctive material: a **pluggable `Foswiki::Store` backend**
(RcsWrap / RcsLite / **PlainFileStoreContrib**) behind a versioned interface, the
`Foswiki::Meta` topic-object indirection, the OO/MVC core rewrite, the cleaner
`Foswiki::Func` + `registerTagHandler` extension API, **DataForms** (+ MetaDataPlugin,
FlexFormPlugin), and the **WysiwygPlugin** TML↔HTML round-trip.

Read through shard-wiki's lens: Foswiki is the engine that **already separates its
store backend from its core via a versioned interface** — i.e. it is concrete prior
art for shard-wiki's own *shard adapter contract* and *capability-aware adapters*.

Pairs with — and deliberately does not repeat — the shared TWiki material:
- `research/260613-twiki-deep-dive/` — flat-file/RCS store, Webs/Topics, plugin
  handler callbacks, per-topic ACL (all inherited; read there for the shared parts)
- `research/260613-xwiki-deep-dive/` — the Java/DB app-platform sibling
- `research/260608-wikiengines-overview/` — landscape scan

## Contents

| Path | Role |
|------|------|
| `findings.md` | Distinctives vs TWiki, store abstraction, extension API, DataForms, capability profile, INTENT mapping, UC seeds, sources |

## Status

Initial deep dive complete. Two new use cases promoted to
`spec/UseCaseCatalog.md` (UC-42, UC-43); UC-34/39/40 enriched. The
`Foswiki::Store`/`Foswiki::Meta` abstraction is logged as adapter-contract prior art
for `workplans/SHARD-WP-0002-federation-architecture.md`.