Domain Modeling

Actively build and sharpen the project's domain model while designing. This is the active discipline — challenging terms, inventing edge-case scenarios, and writing decisions down the moment they crystallise. Merely reading the glossary for vocabulary is a habit any skill can have; this skill is for when the model is changing.

Where things go

docx/
├── glossary.md              ← canonical terms, one project-wide file
└── decisions/
    ├── 0001-event-sourced-orders.md
    └── 0002-postgres-for-write-model.md

Create lazily — no docx/glossary.md until the first term is resolved, no docx/decisions/ until the first ADR earns its place. An empty scaffold is noise. If the repo already keeps decisions elsewhere (docs/adr/, an ADR tool), use that; confirm once at the first write, then stop asking.

The four moves

Challenge against the glossary. When a term conflicts with docx/glossary.md, say so immediately. "The glossary defines cancellation as X, but this reads as Y. Which is it?"

Sharpen fuzzy language. When a term is vague or overloaded, propose a precise canonical one. "You said account — is that the Customer or the User? Those are different things, and the design branches on which."

Cross-reference with the code. When someone states how something works, check whether the code agrees. Surface contradictions rather than silently correcting them. "The plan says partial cancellation is possible, but cancelOrder only handles whole orders. Which is right?"

Write inline. The moment a term settles, append it. Do not batch — the reasoning is only fresh while the discussion is live.

## Cancellation

A customer-initiated reversal of an unfulfilled Order. Distinct from a Refund,
which reverses payment on an Order that already shipped.

docx/glossary.md is a glossary and nothing else — no implementation detail, no spec, no scratch notes. An entry describing how something is built belongs in design.md.

Offer ADRs sparingly

Record a decision only when all three hold:

1. Hard to reverse — changing your mind later carries real cost.
2. Surprising without context — a future reader will ask "why on earth did they do it this way?"
3. A real trade-off — genuine alternatives existed and one was chosen for stated reasons.

Any one missing, skip it. A decisions log padded with obvious choices stops being read.

Write to docx/decisions/NNNN-kebab-slug.md, numbering from the highest existing file. Numbers are permanent addresses — supersede, never renumber.

# NNNN. <Decision title>

- **Status:** accepted
- **Date:** YYYY-MM-DD

## Context

The situation that forced a decision. What constraint made this hard.

## Decision

What was chosen, in the active voice.

## Alternatives considered

Each real option and the specific reason it lost. An ADR with no alternatives
is a note, not a decision record — that was the third test, and it failed.

## Consequences

What this makes easy, what it makes hard, and what would have to be true to
revisit it.

Distinct from post-mortem, which records why something broke. ADRs record why something was chosen.