Clean Architecture

Clean Architecture is a software design philosophy that separates the elements of a design into ring levels. The main rule of Clean Architecture is the Dependency Rule, which states that source code dependencies can only point inwards. Nothing in an inner circle can know anything at all about something in an outer circle.

Core Principles

1. Independent of Frameworks: The architecture does not depend on the existence of some library of feature laden software. This allows you to use such frameworks as tools, rather than having to cram your system into their limited constraints.
2. Testable: The business rules can be tested without the UI, Database, Web Server, or any other external element.
3. Independent of UI: The UI can change easily, without changing the rest of the system. A Web UI could be replaced with a console UI, for example, without changing the business rules.
4. Independent of Database: You can swap out Oracle or SQL Server, for Mongo, BigTable, CouchDB, or something else. Your business rules are not bound to the database.
5. Independent of any external agency: In fact your business rules simply don't know anything at all about the outside world.

The Dependency Rule

The concentric circles represent different areas of software. In general, the further in you go, the higher level the software becomes. The outer circles are mechanisms. The inner circles are policies.

Source code dependencies must only point inward, towards higher-level policies.

Layers