Ubiquitous Language

Ubiquitous Language: Project Thesaurus Manager

You enforce naming consistency across the codebase by maintaining a living thesaurus of domain terms and consulting it every time something needs a name.

Four modes:

• Naming consultation (frequent) — everything in this file
• Thesaurus generation (rare) — read references/generating-thesaurus.md
• Naming audit (periodic) — read references/naming-audit.md
• History mining (optional) — read references/git-history-mining.md when ## Unresolved items need evidence: which name came first, which replaced which, which is dying. Offered after generation, or on demand against an existing thesaurus.

Foundations

This skill combines two bodies of knowledge:

• Domain-Driven Design (DDD) by Eric Evans — ubiquitous language, bounded contexts, aggregate naming
• First Principles Framework (FPF) — a transdisciplinary "operating system for thought" that provides formal tools for semantic precision: bounded contexts as declared semantic frames, polysemy unpacking, lexical firewalls, cross-context bridges with loss notes, term continuity relations, and anti-explosion naming control. References like "FPF F.5" or "FPF A.1.1" point to specific sections of the FPF specification.

Core Principle

"A project should use a single, shared vocabulary. Every name in code, docs, APIs, and conversations must map to a term in the thesaurus. If a concept isn't in the thesaurus — add it before naming anything."

— Domain-Driven Design, Eric Evans

The codebase is primary evidence, not automatic authority. Use code to discover which terms are currently in circulation. Use the thesaurus and user input to decide which terms SHOULD be canonical.

• For what exists today — derive from code (classes, DB schemas, API routes, events)
• For what should become the standard — ask the user/domain expert
• If code contradicts the approved thesaurus — the thesaurus wins for new code
• If the user says "fix legacy naming" — the user's directive overrides the codebase; map existing code names to ## Legacy lines and use the user's terms as canonical

Tacit knowledge: For areas not yet implemented, the most important domain knowledge exists only in experts' heads, not in any artifact.

Thesaurus File

Locating the thesaurus:

1. If the user specified a path — use it
2. If THESAURUS.md already exists somewhere in the repo — use that location
3. Default: docs/THESAURUS.md

Single source of truth for domain vocabulary.

Versioning

The thesaurus declares its format version and the skill that maintains it in YAML frontmatter — machine-readable, outside the body, still one grep away:

---
thesaurus-format: "2.0"
skill: ubiquitous-language
---

# Project Thesaurus

Quote the version — unquoted 2.10 is the YAML float 2.1.

• rg -n '^thesaurus-format:' THESAURUS.md → the version in one hit. No key = 1.0 (the pre-index prose layout shipped before skill 2.0) — unless the file already has - **Term** `Id` kind: Index lines: that is an unstamped 2.0 file from plugin 9.2.0; just add the stamp.
• Format major = skill major (metadata.version in this file's frontmatter). Skill minor/patch releases never change the format.
• Read any format ≤ your own; write only the current one. A major gap means migration first (see generating-thesaurus.md); a minor gap means new optional tokens — older readers keep working, you may add the tokens as you touch lines.
• A thesaurus with a format newer than yours: read it, don't rewrite it — tell the user to update the skill.
• Only the format is versioned in the file. The skill's own version is not recorded there — it would go stale on every edit and git log already answers "who wrote this". skill: is a pointer, so an agent without the skill knows what to install.

Layout: grep-first

The file is designed so that one rg/grep for any name answers "what do I do with this name?" without reading the surrounding text. Five sections, fixed order:

Registry invariant: every name known to the project appears in exactly one registry line — an Index line (as Term, Identifier, or avoid), a Forbidden line, a Legacy line, or an Unresolved header. Each kind of registry line has its own shape, so the shape of the hit tells you its status and the line itself tells you the canonical name. No -B/-A context needed.

Registry lines are bullet lines with labelled tokens, not Markdown tables: tables need | (an alternation in rg), match by column position, and get re-padded by formatters. Tokens (kind:, ctx:, avoid:, use:, in:, →) are position-free, formatter-proof, and need no escaping.

# Project Thesaurus

## Index

- **Order** `Order` kind:aggregate avoid: `Purchase`, `Transaction`, `Buy`
- **Order Line Item** `OrderLineItem` kind:entity avoid: `LineItem`, `OrderItem`, `Item`
- **Order Placed** `OrderPlaced` kind:event avoid: `OrderCreated`, `NewOrder`

## Terms

### Order
- **Definition**: A customer's confirmed request to buy one or more products at agreed prices.
- **NOT**: A payment (that's `Payment`), a shipment, or a draft cart (that's `Cart`).
- **Related**: Order Line Item, Order Placed, Cart

## Forbidden

- `Manager` use: `OrderFulfillment` — hides responsibility; name the activity

## Legacy

- `UserManager` → `Customer` + `CustomerRegistration` in: `src/legacy/` — split in v3

## Unresolved

### Account — one word, two concepts (billing vs auth)
- **Found in**: `billing/Account.ts` (balance), `auth/Account.ts` (login)
- **Question**: Two bounded contexts, or one of them a naming mistake?
- **Impact**: 18 files
- **Options**: `BillingAccount` + `UserAccount`; or contexts Billing / Identity

Index line

- **<Term>** `<Identifier>` kind:<kind> [ctx:<Context>] [avoid: `<name>`, `<name>`]

• One line per concept. All names for that concept live on that line — this is what makes reverse lookup (rg Purchase → "use Order") a single hit.
• Backticks around every identifier-like name. rg '`Order`' is an exact match; rg Order would also hit OrderLineItem and Reorder. rg -F '**Order**' is the exact Term.
• Sorted alphabetically by Term. Entries under ## Terms follow the same order.
• avoid lists live only here. Entries do not repeat them — one place, no drift.

Forbidden and Legacy lines

- `<Word>` use: `<Identifier>`[, `<Identifier>`] — <why>
- `<OldName>` → `<Identifier>`[ + `<Identifier>`] in: <files/modules> — <note>
- `<OldName>` → — (see `<X>`, `<Y>`) in: <files> — retired

use: always points at an Index Identifier. → is the legacy marker: A + B means the old name was split; → — means retired with no single successor.

Entry

### [Term]
- **Definition**: What this concept means in the business domain — one sentence
- **NOT**: What this term does NOT mean; name the neighbouring term it is confused with
- **Related**: Other Index Terms this connects to, written exactly as in the Term field

Optional lines when they carry real information: **Broader**, **Narrower**, **Part of**, **Has parts**, **Example**. Write them on one side only — rg gives the inverse for free, mirrored copies only drift. Minimal viable entry is one line: - **Definition**: … — the Index line already holds the rest.

Anchor grammar (so lookups are one regex): the header is exactly ### <Term> or ### <Term> (<Context>) — nothing else. Tags, status, and context prefixes belong in the Index line, not in the header. Find an entry with rg -n '^### Order( \(|$)' — \b alone is not enough, it would also match ### Order Line Item.

The thesaurus captures concepts, not behavior. It's strong at nouns (entity names, roles, process names) but won't replace behavioral specs for business rules. Don't try to turn the thesaurus into a specification — keep entries short. If a concept has a critical invariant, note it briefly in the definition, not as a separate section.

Non-English domains: If the business domain operates in a non-English language, the Term uses the original language — the thesaurus should reflect how domain experts actually speak. The Identifier carries the code form: - **Счёт-фактура** `Invoice` kind:entity. This is exactly why both fields exist.

Lookup Protocol

Look up before inventing. This is the single most important step. Most naming tasks don't need a new term — the right name is already there.

1. Locate the thesaurus (see above). If absent, tell the user and offer generation. Check rg -n '^thesaurus-format:' — no key or 1.x means the old layout: the protocol below still works by plain text search, but offer migration once, up front.

2. Read the Index if it has ≤ ~60 lines — it is the entire vocabulary at one line per concept, cheaper than any search. For larger files, search instead.

3. Search every candidate name you are considering, plus whatever the surrounding code already calls the thing. Use rg (the Grep tool) or grep -E — same patterns:

   rg -n -i 'invoice' docs/THESAURUS.md             # any role, any section
   rg -n '`OrderLineItem`' docs/THESAURUS.md        # exact identifier as seen in code
   rg -n -F '**Order**' docs/THESAURUS.md           # exact Term (not "Order Line Item")
   rg -n 'avoid:.*`Purchase`' docs/THESAURUS.md     # is this word a banned synonym?
   rg -n 'kind:event' docs/THESAURUS.md             # all terms of one kind
   rg -n 'ctx:Billing' docs/THESAURUS.md            # everything one context owns
   rg -n '`Basket` →' docs/THESAURUS.md             # legacy name and its replacement
   rg -n -A4 '^### Invoice( \(|$)' docs/THESAURUS.md  # the entry itself

   The only trap: * and | are regex metacharacters — use -F for **Term**, and never search for table pipes (there are none).

4. Act on the shape of the line you hit:

   Hit line looks like	Meaning	Do
   - **X** `X` kind:… — your word is the Term or Identifier	Concept exists	Use the Identifier exactly. Stop
   - **X** … avoid: … `your word`	You were about to use a banned synonym	Use that line's Identifier instead
   - `word` use: …	Word is banned from domain names	Pick the Identifier after use:
   - `word` → …	Old name still in code	Use the replacement after → for new code; don't spread the legacy name
   ### word — … under ## Unresolved	Open naming question	Don't decide silently — surface it, ask the user, or offer history mining (see below)
   ### header / entry text only	Related concept	Read the entry; it may inform composition
   No hit	New concept	Go to "If the concept is new"

5. Check the bounded context if Index lines carry ctx: — the same word may be canonical in one context and banned in another.

ALWAYS run this before naming: classes, interfaces, types, enums, aggregates, entities, value objects, functions, methods, commands, queries, domain events, variables, constants, fields, parameters, DB tables/columns/collections, API endpoints and response fields, files, directories, modules, packages, feature flags, config keys, environment variables, and commit messages or PR titles that reference domain concepts.

If the Concept Is New

Before minting a new term, try four levers (from FPF F.14 "Name less, express more"):

1. Reuse — does an existing term already cover this? Maybe the concept is a variant, not a new thing
2. Compose — can you combine existing terms? OrderLineItem reuses Order + LineItem
3. Qualify — is this the same concept in a different state/window? Don't create NightOperator — use Operator with a time qualifier
4. Ask — if still unclear: "I need to name [concept]. The thesaurus doesn't have a term for this. What does the domain call it?" If the user doesn't have an answer either — that's a white spot, not a dead end. Building a ubiquitous language is co-creation, not extraction. Add it to ## Unresolved with a [WHITE-SPOT] tag in the header. Don't force a name for an undefined concept.

Only after all four fail, mint a new term:

1. Name what the invariants make true (FPF F.5) — don't name aspirationally. If the code doesn't enforce "Premium", don't call it PremiumCustomer
2. Use minimal generality — choose the narrowest name whose rules you actually enforce. Don't upgrade Task to Activity to sound universal
3. Keep it to 1-3 words — no rhetorical adjectives ("robust", "optimal", "advanced")
4. Add it to the thesaurus: an Index line (Term, Identifier, kind:, avoid: — omit avoid: when empty) and a ### Term entry with at least a Definition. Keep both sorted
5. Then use the term in code

If You Find an Inconsistency

When existing code uses a term that contradicts the thesaurus:

• Flag it: "Found fetchPurchases() but the Index line says Order, with Purchase under avoid:"
• Suggest a rename if scope is small
• For large-scale renames, note as tech debt and ask user how to proceed