samuelho-dev/dev-config/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 the canonical domain glossary 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

First inspect project instructions and existing domain documents, including GLOSSARY.md/GLOSSARY-MAP.md, CONTEXT.md/CONTEXT-MAP.md and the documented ADR directory. Follow the established canonical documents and their links; these filenames are conventions, not portable Agent Skills requirements. If both forms exist, use documented authority; if authority is unclear, ask before writing. Never create a second competing glossary/map or rename consumer files as an implicit migration.

The CONTEXT names below are this curated collection's fallback only when the project has no established convention. Current upstream uses GLOSSARY names; retaining this local default does not claim upstream identity. Use the selected canonical glossary throughout the session, not the fallback filename.

A single-context fallback looks like:

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

For multiple contexts, follow the canonical map's links. The curated fallback map is CONTEXT-MAP.md, which points to each context's glossary:

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

Create files lazily, only after resolving canonical ownership. When no domain convention exists, create the fallback CONTEXT.md for the first resolved term. Follow the established ADR directory; docs/adr/ is only the fallback 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 the canonical glossary, 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 the canonical glossary inline

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

Keep new glossary entries focused on domain language; record implementation decisions in the project's ADRs/specs. An existing CONTEXT.md may serve a broader project purpose: preserve that content and follow the project's actual glossary location rather than deleting non-glossary material to impose this collection's format.

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. Use the format in ADR-FORMAT.md.