What relationships and responsibilities should exist between layers in an architecture based on the principles of clean architecture?

In clean architecture, layers are separated by responsibility and dependency direction:

• External layers (e.g., UI, databases) depend on internal ones, but not vice versa.
• Internal layers (e.g., business logic, domain model) should not know about external implementation details.

Responsibilities and relationships:

1. Entities — contain business rules and models. They depend on nothing.
2. Use Cases — implement specific business processes, use entities.
3. Interface Adapters — transform data between layers, e.g., presenters, repositories.
4. Frameworks & Drivers — external components, UI, databases.

The dependencies point inward: the outer layer depends on the inner one, not the other way around. This ensures the independence of business logic from UI and infrastructure, facilitating testing and maintenance.