Domain Driven Design Guidelines

ddd-guidelines.md

• Aggregate roots should not refer to any other aggregate roots, even in the constructor. Only the id of related aggregate roots is allowed.
• Constructors can only accept ids and value types.
• No setter properties are allowed. Use only methods for mutating state.
• All business rules should be coded in the aggregate roots. Querying is the only type of "business rules" that are allowed outside of aggregate roots.
• Use domain events to signal events in the domain. This is how related aggregate roots can get notified of what happens in other aggregate roots.
• Log all non-standard exits from aggregate root methods. For example, return statements in the middle must have a logging statement that explains the decision to exit.