domain-modeling

Domain Modeling

Actively build and sharpen the project's domain model as you design. This is the active discipline — challenging terms, inventing edge-case scenarios, and writing the glossary and decisions down the moment they crystallise. (Merely reading GLOSSARY.md for vocabulary is not this skill — that's a one-line habit any skill can do. This skill is for when you're changing the model, not just consuming it.)

File structure

Most repos have a single context:

/
├── GLOSSARY.md
├── docs/
│   └── adr/
│       ├── 0001-event-sourced-orders.md
│       └── 0002-postgres-for-write-model.md
└── src/

If a GLOSSARY-MAP.md exists at the root, the repo has multiple contexts. The map points to where each one lives:

/
├── GLOSSARY-MAP.md
├── docs/
│   └── adr/                          ← system-wide decisions
├── src/
│   ├── ordering/
│   │   ├── GLOSSARY.md
│   │   └── docs/adr/                 ← context-specific decisions
│   └── billing/
│       ├── GLOSSARY.md
│       └── docs/adr/

Create files lazily — only when you have something to write. If no GLOSSARY.md exists, create one when the first term is resolved. If no docs/adr/ exists, create it when the first ADR is needed.

Legacy name. Repos set up before this convention carry CONTEXT.md / CONTEXT-MAP.md (the upstream mattpocock/skills name until 1.3.0). Read either name; when a legacy file exists, keep writing to it rather than creating a second glossary beside it, and offer a git mv to the new name once.

During the session

Challenge against the glossary

When the user uses a term that conflicts with the existing language in GLOSSARY.md, call it out immediately. "Your glossary defines 'cancellation' as X, but you seem to mean Y — which is it?"

Sharpen fuzzy language

When the user uses vague or overloaded terms, propose a precise canonical term. "You're saying 'account' — do you mean the Customer or the User? Those are different things."

Discuss concrete scenarios

When domain relationships are being discussed, stress-test them with specific scenarios. Invent scenarios that probe edge cases and force the user to be precise about the boundaries between concepts.

Cross-reference with code

When the user states how something works, check whether the code agrees. If you find a contradiction, surface it: "Your code cancels entire Orders, but you just said partial cancellation is possible — which is right?"

Update GLOSSARY.md inline

When a term is resolved, update GLOSSARY.md right there. Don't batch these up — capture them as they happen. Use the format in GLOSSARY-FORMAT.md.

GLOSSARY.md carries no implementation details. Do not treat GLOSSARY.md as a spec, a scratch pad, or a repository for implementation decisions. It is a glossary and nothing else.

Offer ADRs sparingly

Only offer to create an ADR when all three are true:

1. Hard to reverse — the cost of changing your mind later is meaningful
2. Surprising without context — a future reader will wonder "why did they do it this way?"
3. The result of a real trade-off — there were genuine alternatives and you picked one for specific reasons

If any of the three is missing, skip the ADR. In orc, ADRs are authored via the orc:adr-writing template into docs/adr/NNNN-*.md — see ADR-FORMAT.md for the lightweight shape and what qualifies, and orc:adr-writing for the full house template.