Backlinks and knowledge graph

Premise

Reverse navigation and a view of connected pages are properties of the link graph, not of [[wikilink]] spelling. Hugo already accepts ordinary Markdown links and ref / relref. OINK can derive a graph from content authors already write, without adding a parser, Goldmark extension, or parallel authoring syntax.

The first value is backlinks, not visualization. A static inbound-link list is useful without JavaScript and can degrade into print and Markdown. An interactive graph remains an optional enhancement over that complete list.

Goals and non-goals

Goals:

• derive one language-local link index per build;
• show deterministic inbound links on a page;
• optionally show a bounded local neighbourhood;
• optionally publish a whole-site view and a machine-readable graph;
• preserve ordinary preview when an edited link is stale or incomplete.

Non-goals:

• introducing [[wikilink]] syntax;
• indexing external, mailto:, same-page anchor, or self links;
• executing JavaScript to discover links already present in content;
• turning a visualization into the only way to navigate;
• promising perfect extraction from arbitrary shortcode parameters or raw HTML.

Delivery stages

Each stage is accepted separately. G1 does not wait for G2, and G2 does not force every page to load graph code.

Extraction contract

The proposed index scans source content once per language and records one edge per source/target pair. It strips fenced code and inline code before extracting ordinary Markdown links and ref / relref; then it resolves only internal pages, removes fragments for page identity, drops self-links, and deduplicates repeated references.

The implementation must test at least:

• duplicate links collapse to one edge;
• fenced and inline code produce no edge;
• external, protocol-relative, mail, same-page anchor, and self links are excluded;
• ref and relref are included;
• each language produces an independent graph;
• an unresolved derived edge warns or is reported by the focused checker without making ordinary hugo server unusable.

Raw source scanning has known omissions. A URL stored in a custom shortcode parameter or raw <a href> may not appear. Those omissions must be documented instead of hidden behind a claim of a complete semantic graph.

Backlink output

G1 renders an aside group in the right rail, a sibling of the table of contents and the taxonomy clouds: what is on this page beside what points at this page. The group is expanded by default and shows the first eight entries; the rest fold behind a native disclosure so a heavily referenced page cannot swallow the rail. The switch is the site key params.ui.backlinks (bare boolean, default off); a page overrides it with the prefix-free front matter key backlinks, and a section can cascade it. Order is deterministic: the stable page path — language-independent, naturally grouped with navigation, and needing no second ordering authority. The group uses ordinary links and is omitted when there are no inbound pages.

Unresolvable derived edges are dropped silently and recorded as a known gap: G1 is a local navigation enhancement, not a link checker, and having it report broken links for the site would only duplicate warnings.

Print and Markdown keep the readable list. RSS omits it unless feed-level research demonstrates that backlinks improve an article feed rather than creating noisy site navigation.

Interactive graph boundary

G2 reuses the locally vendored ECharts graph series. The current page is the centre; direct inbound and outbound neighbours form the default depth. A hard node cap prevents unreadable or expensive views. Keyboard focus, text alternatives, reduced motion, forced colours, narrow screens, and print are acceptance requirements, not later polish.

If JavaScript or ECharts is unavailable, G1 remains complete and visible. The runtime is loaded only on pages that render a graph and must join the existing feature-bundle key so unlike pages cannot collide in the asset cache.

Global output

G3 may add a dedicated graph page and an opt-in JSON output. The JSON schema would contain a version, language, nodes, and directed edges with stable URLs; it would not expose local file paths or unpublished pages. The output must be derived from the same index as G1 and G2 so three representations cannot drift.

Compatibility and migration

Ordinary Markdown remains unchanged, so content migration is unnecessary. Configuration names remain undecided until a prototype proves the smallest surface. The default for every interactive or global output is off; a static backlink list may be considered separately because it is local navigation with no network or browser state.

Acceptance criteria

Acceptance requires a focused graph checker, extraction fixtures, HTML/Print/ Markdown goldens, strict-build negative cases, browser accessibility and responsive tests, and a real bilingual-site build. Performance is measured on a representative large site, but a dated prototype timing is not a permanent budget.

Open decisions

Every G1 question is resolved (see the decision log). Still open, and owned by G2/G3:

1. Does the local graph expose one depth or a tightly capped second depth?
2. Which page metadata, if any, is useful enough to enter graph JSON?
3. Is G3 useful enough to justify a new output format before G1 and G2 have production evidence?

Decision log

• 2026-08-19: Drafted the three-stage design.
• 2026-08-27: Resolved and accepted G1, scheduled for OINK 0.8.0. G1 is opt-in: the site key params.ui.backlinks is a bare boolean defaulting to off, pages override with backlinks, and no shell-type gating — policy belongs to the site and the page, not the shell. Ordering simplifies to a single stable-page-path sort, dropping the section → weight → title chain: one deterministic authority is enough for reverse navigation, and a multi-level sort would be a second navigation authority. Unresolvable edges drop silently and are recorded as a known gap, never warned. G2/G3 and the graph data output keep waiting for production evidence.
• 2026-08-27: Design review moved the block from the page end to the right rail. Backlinks are page metadata and pair with the table of contents, while the page end is the reader’s completion zone — share, feedback, provenance, pager, comments. The rail group also adds the eight-entry cap, with the rest behind a native disclosure.