Domain-Driven Design helps build software that matches business complexity. It's about understanding the domain deeply and reflecting that understanding in code.
Core Concepts
Strategic Design:
- Bounded Context: Clear boundaries around domain models
- Ubiquitous Language: Shared vocabulary between devs and domain experts
- Context Mapping: Relationships between bounded contexts
Tactical Design:
- Entities: Objects with identity
- Value Objects: Objects defined by attributes
- Aggregates: Consistency boundaries
- Domain Events: Significant occurrences
- Repositories: Data access abstraction
Bounded Contexts
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Entities and Value Objects
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Aggregates
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Domain Events
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Repositories
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Application Services
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Best Practices
Modeling:
✓ Model the domain, not the database
✓ Use ubiquitous language consistently
✓ Keep aggregates small
✓ Protect invariants in aggregate roots
Implementation:
✓ Make implicit concepts explicit
✓ Use value objects for domain concepts
✓ Raise domain events for side effects
✓ Isolate domain from infrastructure
Organization:
✓ One aggregate per transaction
✓ Reference aggregates by ID
✓ Use domain events for cross-aggregate consistency
✓ Keep bounded contexts independent
Conclusion
DDD helps manage domain complexity by aligning code with business concepts. Start with bounded contexts and ubiquitous language. Use aggregates to enforce invariants and domain events for loose coupling. The investment pays off in maintainability and clarity.