ddd

Domain-Driven Design (DDD) Reference

Reference guide to Domain-Driven Design (DDD) and Clean/Modular Architecture. Provides a structured taxonomy of strategic design, tactical patterns, clean layering, CQRS, and specifications to align software construction with business domains.

Quick Decision Trees

"I am designing system boundaries or modeling business concepts"

Which strategic task?
├─ Discovering subdomains and capabilities → strategic-design.md
├─ Designing bounded contexts and vocabulary → strategic-design.md
└─ Mapping context interactions (ACL, Partnership, etc.) → strategic-design.md

"I am writing domain objects and code structures"

Which tactical/architectural task?
├─ Modeling aggregates, entities, and value objects → tactical-patterns.md
├─ Separating application and domain logic → clean-architecture.md
├─ Defining repository contracts or domain services → tactical-patterns.md
└─ Structuring presentation and infrastructure layers → clean-architecture.md

"I am refactoring queries, validations, or legacy code"

Which refactoring task?
├─ Separating read paths and write paths (CQRS) → cqrs-pattern.md
├─ Encapsulating business rules (Specifications) → specification-pattern.md
└─ Refactoring legacy CRUD to modular monoliths → legacy-modular-systems.md

DDD Knowledge Index

1. Strategic Design

Topic	Reference Document	Description / Keywords
1.1 Ubiquitous Language	strategic-design.md	Shared vocabulary, glossary, terminology alignment
1.2 Subdomains	strategic-design.md	Core, Supporting, and Generic subdomain categorization
1.3 Bounded Contexts	strategic-design.md	Semantic boundaries, modular design, single team ownership
1.4 Context Mapping	strategic-design.md	Integration contracts, ACL, Partnership, Shared Kernel, Conformist

2. Tactical Patterns

Topic	Reference Document	Description / Keywords
2.1 Entities and Value Objects	tactical-patterns.md	Identity-driven objects, immutable value objects, structural equality
2.2 Anemic vs. Rich Models	tactical-patterns.md	Transitioning property bags to behavior-encapsulated models
2.3 Aggregates and Invariants	tactical-patterns.md	Consistency boundaries, aggregate roots, transactional boundaries
2.4 Domain Services	tactical-patterns.md	Stateless operations spanning multiple aggregates

3. Clean Layering

Topic	Reference Document	Description / Keywords
3.1 Four Architecture Layers	clean-architecture.md	Presentation, Application, Domain, and Infrastructure roles
3.2 Inward Dependency Flow	clean-architecture.md	Dependency rules, shielding the domain model from tech volatility
3.3 Persistence Ignorance	clean-architecture.md	Separating Domain Models from database-optimized Data Models

4. Advanced Refactoring

Topic	Reference Document	Description / Keywords
4.1 CQRS Pattern	cqrs-pattern.md	Command-Query Separation (CQS), Task-Based UI, Mediator, Handler segregation
4.2 Specification Pattern	specification-pattern.md	Encapsulating reusable query, validation, and object creation rules
4.3 Legacy and Monoliths	legacy-modular-systems.md	Refactoring legacy systems, modular monolith design, software architecture Zen

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