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diagram-design/docs/adr/0002-semantic-patterns-do-not-expand-the-taxonomy.md
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4691a2f40c feat(types): ship ten editorial diagram types in one release (#118)
Adds ten editorial diagram types with light, dark, and full-editorial examples; updates the taxonomy, gallery, descriptions, references, and synchronized plugin version; and adds maintainer/visual-proof contribution gates.

Co-authored-by: Jacopo Vendramin <vendraminjacopo@gmail.com>
2026-08-19 15:49:27 -07:00

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ADR 0002 — Semantic patterns never expand the visual-type taxonomy

Status: accepted (v2.3)

Context

Auditing behavior-rich figures (queues, policy traces, trust boundaries) showed the skill could arrange boxes but not model system behavior. The obvious fix — new diagram types — would balloon the taxonomy, dilute the selection guide, and force every new behavior into a new layout grammar.

Decision

Behavior is a separate axis. The seven semantic patterns in references/semantic-patterns.md each route to the nearest existing visual type for layout; a pattern owns semantic primitives and a tighter budget, never a second layout grammar. The visual-type count only moves when a genuinely new layout grammar appears (it did in v2.5.10 — see ADR 0007, 28 → 38).

Consequences

  • The visual-type count is a stable, verifiable claim (verify-semantic-motion.py and verify-docs-sync.py both count it) — 27 when this record was accepted; see Amendments for the current figure.
  • A new behavior costs one pattern section plus a routing-table row — not a new type reference, template set, and example triple.
  • If a pattern ever needs a layout no existing type provides, that is the signal to add a type, with the full §10 shipping set.

Amendments

2026-08-18 — the count is 28. Treemap was admitted under the escape clause above: recursive area subdivision is a layout grammar no existing type provides (bar encodes with length, nested with containment and no quantity, pyramid with rank). It shipped the full §10 set, and the counters named above moved 27 → 28 together with the prose.

The decision itself is unchanged — semantic patterns still never add a type, and the count still moves only for a new layout grammar. What this amendment records is the procedure: the two counters are this ADR's enforcement, so a PR that edits them without amending this file has quietly made itself the authority. Amend here in the same PR, or the number in the test is just whatever the last contributor typed.

2026-08-19 — the count is 38. Ten additional visual grammars were admitted under the same escape clause: Sankey, fishbone, Wardley map, kanban, user journey, deployment, dependency graph, UML class, story map, and database schema. The per-type argument is in ADR 0007; each ships the full §10 set, and the two counters move 28 → 38 together with the prose.