Tactical DDD — Rich Domain Modeling

Workflow

Determine the user's intent first:

Intent	Phases to run
"validate / review / check / is this correct?"	Phase 1 + 2 only → report findings, ask before refactoring
"fix / refactor / improve / clean up"	Phase 1 + 2 + 3
"how should I design / model this?"	Load reference.md directly

Phase 1 — Detect

Load detection.md and scan the target code for anemia signals. Produce a severity score and list of affected classes.

Phase 2 — Assess

For each affected class, determine the correct building block:

Has unique identity tracked over time?	Has invariants tying multiple objects?	→ Building Block
Yes	—	Entity
No	—	Value Object
Yes (root) + children with shared invariants	Yes	Aggregate
Operation spans multiple Aggregates/doesn't belong to any	—	Domain Service

Prefer Value Objects over Entities. Prefer small Aggregates over large ones.

If intent was validate/review: stop here. Report findings using the output format below. Ask "Would you like me to apply these fixes?" before proceeding.

Phase 3 — Refactor

Load refactoring.md for step-by-step moves. Apply in this order:

1. Replace setter chains with a single expressive method
2. Move service logic into the Aggregate that owns it
3. Add business guards at the top of each method
4. Publish a Domain Event after each successful state change
5. Replace primitive types with Value Objects

For deep pattern questions (boundary design, event modeling, service vs. entity decision), load reference.md.

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Quick Anemia Signals (scan first)

public setX() / public setY()        → behaviour should be encapsulated
service.doX(entity, ...)              → logic likely belongs in entity
entity.setA(); entity.setB(); ...     → setter chain = missing intent method
no domain methods beyond getters      → pure data bag

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Golden Rules

1. Behaviour with data — Objects own both state and the operations that change it
2. Ubiquitous Language — Method names come from the domain, not CRUD (commitTo, not setStatus)
3. Small Aggregates — Root + Value Objects by default; add child Entities only for true invariants
4. One transaction = one Aggregate — Cross-Aggregate rules use eventual consistency via Domain Events
5. Reference by ID — Never hold object references to other Aggregates
6. Value Objects first — Use Entities only when individual identity is essential
7. Domain Services sparingly — Excessive services → anemic model
8. Protect invariants — The Aggregate is the last line of defence; never trust the caller

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Output Format

When reviewing code, report:

## Anemia Diagnosis: <ClassName>

Severity: [None | Mild | Moderate | Severe]

Issues:
- <description of problem>

Recommended refactoring:
- <specific move from refactoring.md>

When refactoring, show a before/after diff for each class touched.