Domain-Driven Design (DDD)
Domain-Driven Design (DDD)
→ Domain-Driven Design (DDD) is an approach to software design that focuses on modeling software around real business domains.
→ The goal is to align code structure with business concepts, making systems easier to understand, evolve, and maintain.
→ It emphasizes collaboration between developers and domain experts.
Core Concepts
➤ Domain
→ The real-world problem space the software is solving.
→ Example: e-commerce, banking, healthcare.
➤ Subdomain
→ A smaller part of the domain.
→ Core Subdomain → What gives the business its competitive advantage.
→ Supporting Subdomain → Helps the core but isn’t unique.
→ Generic Subdomain → Common functionality (auth, logging).
➤ Ubiquitous Language
→ A shared language used by developers and business experts.
→ The same terms appear in conversations, documentation, and code.
→ Reduces misunderstanding and mismatched logic.
➤ Bounded Context
→ A clear boundary where a specific domain model applies.
→ Same term can mean different things in different contexts.
→ Prevents large, tangled domain models.
➤ Entities
→ Objects with a distinct identity that persists over time.
→ Example: User, Order, Account.
➤ Value Objects
→ Objects defined only by their values.
→ Immutable and have no identity.
→ Example: Money, Address, Email.
➤ Aggregates & Aggregate Roots
→ A cluster of related entities and value objects.
→ Aggregate Root controls access and consistency.
→ Example: Order (root) → OrderItems.
➤ Repositories
→ Provide methods to access and store aggregates.
→ Hide database details from the domain logic.
➤ Domain Services
→ Handle domain logic that doesn’t naturally fit inside an entity.
→ Focused purely on business rules.
Flow (High-Level)
→ User Action → Application Layer → Domain Model (Entities, Aggregates, Services) → Repository → Database
→ Business rules live inside the domain, not in controllers or UI.
Benefits
→ Strong alignment between business and code.
→ Easier to scale and evolve complex systems.
→ Improved maintainability for large applications.
→ Clear boundaries reduce coupling.
Drawbacks
→ Requires deep understanding of the domain.
→ Higher upfront design effort.
→ Overkill for small or simple applications.
When to Use
→ Complex business domains.
→ Long-lived enterprise systems.
→ Large teams working on different parts of the same system.
→ Systems where business rules change frequently.
→ The goal is to align code structure with business concepts, making systems easier to understand, evolve, and maintain.
→ It emphasizes collaboration between developers and domain experts.
Core Concepts
➤ Domain
→ The real-world problem space the software is solving.
→ Example: e-commerce, banking, healthcare.
➤ Subdomain
→ A smaller part of the domain.
→ Core Subdomain → What gives the business its competitive advantage.
→ Supporting Subdomain → Helps the core but isn’t unique.
→ Generic Subdomain → Common functionality (auth, logging).
➤ Ubiquitous Language
→ A shared language used by developers and business experts.
→ The same terms appear in conversations, documentation, and code.
→ Reduces misunderstanding and mismatched logic.
➤ Bounded Context
→ A clear boundary where a specific domain model applies.
→ Same term can mean different things in different contexts.
→ Prevents large, tangled domain models.
➤ Entities
→ Objects with a distinct identity that persists over time.
→ Example: User, Order, Account.
➤ Value Objects
→ Objects defined only by their values.
→ Immutable and have no identity.
→ Example: Money, Address, Email.
➤ Aggregates & Aggregate Roots
→ A cluster of related entities and value objects.
→ Aggregate Root controls access and consistency.
→ Example: Order (root) → OrderItems.
➤ Repositories
→ Provide methods to access and store aggregates.
→ Hide database details from the domain logic.
➤ Domain Services
→ Handle domain logic that doesn’t naturally fit inside an entity.
→ Focused purely on business rules.
Flow (High-Level)
→ User Action → Application Layer → Domain Model (Entities, Aggregates, Services) → Repository → Database
→ Business rules live inside the domain, not in controllers or UI.
Benefits
→ Strong alignment between business and code.
→ Easier to scale and evolve complex systems.
→ Improved maintainability for large applications.
→ Clear boundaries reduce coupling.
Drawbacks
→ Requires deep understanding of the domain.
→ Higher upfront design effort.
→ Overkill for small or simple applications.
When to Use
→ Complex business domains.
→ Long-lived enterprise systems.
→ Large teams working on different parts of the same system.
→ Systems where business rules change frequently.
Source: Dhanian
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