| name | ubiquitous-language |
| description | One ubiquitous language per bounded context — mechanically enforced, evolving only by decision. Per-context Contextive-format glossaries reconciled against code by lint; the five-step language protocol (detect, propose, decide, record, rename) for every new or changed domain term; glossary-driven identifier and test-title checking. Use when naming domain concepts, when a term is missing from or fights the glossary, when spotting synonyms or near-duplicates, when bootstrapping a glossary, or when renaming across a bounded context. For DDD building blocks see domain-driven-design; for acceptance-DSL vocabulary see acceptance-testing. |
Ubiquitous Language: Evolution by Decision, Never Drift
A change in the language is a change to the model (Evans). One ubiquitous language per bounded context — apply a single language to a whole enterprise and you will fail (Vernon). This skill makes the language a first-class, mechanically-enforced artifact that is expected to evolve — but only ever through an explicit, recorded decision.
The documented agent failure mode this kills: terminology drift — processUserData vs processUserInfo near-duplicates, "booking" quietly becoming "reservation" mid-feature. Prompt-level glossaries steer; deterministic gates enforce.
| Resource | Load when... |
|---|
resources/language-protocol.md | A term is missing, awkward, or duplicated — running the five steps, writing Y-statement micro-ADRs |
resources/glossary-format.md | Creating or editing a glossary — Contextive YAML format, context scoping, aliases, bootstrap paths |
Where the Language Lives (priority order)
Team speech and the model in the code are the only guaranteed-current denotation of the language (Vernon). So:
- Domain code — identifiers and branded types ARE the language.
CustomerId, Receipt, placeOrder. Branded types are the positive enforcement: the only way to obtain a CustomerId is the named parse, so primitives can't smuggle anonymous concepts through the domain.
- The acceptance harness — DSL verbs and test titles are the executable ubiquitous language. Write for the least technical person who understands the problem domain (Farley); test names as domain sentences is the founding move of BDD (North).
- The glossary — the index, not the source of truth. Per bounded context, in the repo, riding PR review:
<context>.glossary.yml in Contextive format (LSP-based hover definitions in every major editor; folder scoping maps onto bounded contexts). A glossary that isn't reconciled against code rots — this one is lint-checked against the code, which is precisely what makes it living.
The Language Protocol (the centrepiece)
Silent evolution is forbidden. Every new, changed, or suspect domain term runs five steps — full guidance in resources/language-protocol.md:
- DETECT — you need a term the glossary lacks; you spot a synonym or near-duplicate (one word per concept; two phrases must mean two concepts); a term feels awkward in conversation; or the identifier lint fails on an unknown domain word.
- PROPOSE — never adopt. STOP and present to the human: the term, a proposed definition, the bounded context, an example sentence, and the alternatives considered. Use the harness's question mechanism with a recommendation attached. An agent never coins a domain term silently.
- DECIDE — the human approves, renames, or rejects. Cheap because it's one term at a time with a recommendation.
- RECORD — glossary entry added or updated in the same PR; replaced terms become deprecated
aliases (so lints can name the replacement). Renames that change the model, not just a label, get a Y-statement micro-ADR; routine additions need only the glossary diff.
- RENAME — in that order: decision first, then refactor code, tests, and glossary together in one atomic PR. Boundary rule: rename freely inside the bounded context; the published language at context boundaries — APIs, events, schemas — is versioned deliberately, never casually renamed.
Mechanical Enforcement
Where a mechanical enforcement layer is installed (lint rules generated from the glossary), it runs inside the agent's loop, scoped to domain paths — and enforces:
- Banned vocabulary — weasel suffixes in domain code (
Info, Base, Item, Manager, Helper, Util, Data, Processor, Impl, …): these names mean the concept hasn't been found yet.
- Glossary-driven identifier check (the flagship, novel-in-TypeScript rule) — split identifiers into words; validate domain words against the context's glossary using token classes: glossary terms / deprecated aliases (flagged with their replacement) / path-scoped technical stopwords / exempt framework identifiers.
- Test-title check — titles validated against the glossary; deprecated aliases rejected naming the canonical replacement.
- DSL vocabulary check — a new acceptance-DSL verb either exists in the glossary or triggers the protocol.
- Structural rules — pure-domain-core dependency rules (no domain→app, no domain→infra except ports, no framework imports in domain).
Every rule teaches: three-part messages — what fired, why the rule exists, what to do instead, with a skill pointer. A gate with no exit invites bypass, so the documented-exception process (justified in the PR, recorded) stays open.
Enforcement status: until a generated lint layer or equivalent gate is installed in the project, everything here is convention — say so; never imply protection that isn't there. The protocol and glossary stand on their own; enforcement is an amplifier, not a prerequisite.
The Adoption Spectrum
- Greenfield — full rule set from commit one; the walking skeleton is the first passenger.
- Brownfield — the protected-core ratchet. You cannot lint your way to hexagonal in a big ball of mud: a rule that fires 4,000 times on day one is deleted on day two. Instead declare a nearly-empty
domain/ core and enforce its purity from day one; legacy stays legally messy outside but reaches in only through ports; every slice touching legacy business logic moves that logic into the core (Strangler Fig). Pre-existing violations freeze in a baseline whose counter may only go down. The glossary rolls out the same way: warn-first, diff-scoped, until it matures.
- Spikes — the declared spike marker exempts language and architecture rules, except quarantine, which never turns off. Vocabulary discovered in a spike enters the glossary through the protocol at promotion time, not during the spike.
Boundaries
| Situation | Skill |
|---|
| Value objects, entities, aggregates, bounded contexts | domain-driven-design |
| Ports/adapters structure the arch rules enforce | hexagonal-architecture |
| DSL and test-title vocabulary in the outer loop | acceptance-testing |
| Recording a model-changing rename | adr agent (Y-statement template) |
| Naming questions during authoring-loop interrogation | grill-me (A3) |
Verification Checklist
