Domain-Driven Design

Developers model a complex business using technical concepts: CustomerTable StatusCode ProcessFlag But business experts talk about contracts, claims, policies and renewals. The software and business describe different worlds.

Model software around business concepts and language. Policy Claim Coverage Renewal With data-only models, the application layer holds the business rules. A rich DDD model keeps rules with the data: Order.Cancel() enforces cancellation rules, while the application layer loads the order, calls Cancel(), and saves it. Onion and Clean Architecture organize dependencies and can support either model style. DDD focuses on business meaning, rules, and boundaries. The distinction is data-only versus behavior-rich models.