Domain Driven Design

---
name: domain-driven-design
description: 'Model software around the business domain using bounded contexts, aggregates, and ubiquitous language. Use when the user mentions "domain modeling", "bounded context", "aggregate root", "ubiquitous language", "anti-corruption layer", "context mapping", "domain events", "strategic design", "the code doesnt match the business", or "how do we split this big system". Also trigger when breaking a monolith into services, defining service boundaries, or aligning code structure with business processes. Covers entities vs value objects, domain events, and context mapping strategies. For architecture layers, see clean-architecture. For complexity, see software-design-philosophy.'
license: MIT
metadata:
  author: wondelai
  version: "1.4.0"
---

# Domain-Driven Design Framework

Framework for tackling software complexity by modeling code around the business domain. The greatest risk in software is not technical failure -- it is building a model that does not reflect how the business actually works.

## Core Principle

**The model is the code; the code is the model.** Software should embody a deep, shared understanding of the business domain. When domain experts and developers speak the same language and that language is directly expressed in the codebase, complexity becomes manageable and the system evolves gracefully as the business changes.

## Scoring

**Goal: 10/10.** Score a domain model by awarding **1 point per satisfied row of the Quick Diagnostic** (7 rows) plus up to 3 points for depth: +1 if the Core Domain has a genuinely rich model (not just CRUD), +1 if invariants live inside aggregates rather than in services, +1 if the ubiquitous language is consistent across conversation, code, and tests. Bands: **9-10** = expert-readable names, explicit context boundaries with ACLs, small aggregates, behavior-rich entities, events for cross-aggregate flow, an identified Core Domain; **5-6** = some domain language but leaky boundaries or anemic objects; **<=3** = technical naming, one model for everything, logic scattered in services. Report the score and the specific diagnostic rows failing.

## Framework

### 1. Ubiquitous Language
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