| name | domain-modeling |
| description | Build and sharpen a project's domain model. Use when the user wants to pin down domain terminology or a ubiquitous language, record an architectural decision, or when another skill needs to maintain the domain model. |
| metadata | {"inspired-by":"https://github.com/mattpocock/skills/blob/main/skills/engineering/domain-modeling/SKILL.md"} |
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 CONTEXT.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
Expect the following structure using arc42.
/
├── docs/
│ └── arc42/
Create files lazily — only when you have something to write. If no docs/arc42/12-glossary/doc-12001-terms.adoc exists, create one when the first term is resolved. If no docs/arc42/09-architecture-decisions/ exists, create it when the first ADR is needed.
During the session
Challenge against the glossary
When the user uses a term that conflicts with the existing language in docs/arc42/12-glossary/doc-12001-terms.adoc, call it out immediately. "Your ubiquitous language and 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?"
Offer ADRs sparingly
Only offer to create an ADR when all three are true:
- Hard to reverse — the cost of changing your mind later is meaningful
- Surprising without context — a future reader will wonder "why did they do it this way?"
- 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.
Creating an ADR
To create an ADR use the /adr skill.
Architecture Artifact Metadata
When domain-modeling work creates or changes arc42 source artifacts, ADRs,
glossary documents, relations, or other architecture metadata, read and apply
../../src/docs/arc42/04-solution-strategy/doc-04001-metamodel.adoc when it is available.
Keep metadata and relation semantics aligned with the architecture metamodel
instead of inventing local conventions.
