# Nw Ddd Tactical

Tactical DDD, aggregate design rules, entities, value objects, domain events...

- Repository: https://github.com/nWave-ai/nWave (628 stars)
- Category: Design
- License: MIT
- Last updated: 2026-09-16
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add nWave-ai/nWave --skill nw-ddd-tactical -g -a claude-code -y`
Codex: `npx skills add nWave-ai/nWave --skill nw-ddd-tactical -g -a codex -y`
Cursor: `npx skills add nWave-ai/nWave --skill nw-ddd-tactical -g -a cursor -y`
Gemini CLI: `npx skills add nWave-ai/nWave --skill nw-ddd-tactical -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add nWave-ai/nWave`

## Description

Tactical DDD, aggregate design rules, entities, value objects, domain events, repositories, domain services, and anti-pattern detection

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Tactical DDD

Implementation patterns within a bounded context. Tactical DDD answers: "How do we structure the domain model?"

## Aggregates

An aggregate is a consistency boundary -- a cluster of domain objects that must be transactionally consistent.

### Vernon's Four Design Rules

1. **Model true invariants in consistency boundaries**: Only include elements that MUST be consistent within the same transaction. If two entities don't share an invariant, they belong in separate aggregates.

2. **Design small aggregates**: ~70% of aggregates contain only a root entity with value-typed properties. Large aggregates create concurrency contention, scalability failures, and memory pressure.

3. **Reference other aggregates by identity**: Use `ProductId` not `Product`. Direct object references create accidental cross-aggregate transactions and prevent independent scaling.

4. **Use eventual consistency outside the boundary**: Domain events communicate across aggregates. One transaction = one aggregate. If you need to update two aggregates "atomically," reconsider your boundaries.

### Aggregate Design Checklist

- [ ] Contains only elements sharing true invariants
- [ ] Root entity controls all access (no direct child manipulation)
- [ ] External references by ID only (no object graphs)
- [ ] Small enough for single-transaction performance
- [ ] Command produces events (in event-sourced systems) or mutates state (in traditional)
- [ ] Business rules validated in command handling, not in persistence layer

### Common Aggregate Smells

The rest: https://github.com/nWave-ai/nWave/blob/HEAD/nWave/skills/nw-ddd-tactical/SKILL.md