Representational state transfer (REST) is a style of software design architecture.

In order to be RESTful, the architecture must comply to the following contraints.

1. Client-server:
   • Separation of concerns into client and server (loose coupling):
     • Client focuses on UI
     • Server not concerned about UI
2. Stateless:
   • No client context is stored on the server between requests.
   • All session state is stored in client.
   • Server can be stateful, but every server side state need to be addressable by URL as a resource.
3. Cacheable:
   • All responses must indicate to client if they are cacheable.
4. Layered system:
   • Client does not know about the end server (Allow intermediary servers)
5. Code on demand (optional):
   • Servers can temporarily extend or customize the functionality of a client by transferring logic (e.g. JavaScript) to the client.
6. Uniform interface
   • Uniform interface decouples client and server to achieve separation of concerns.

RESTful web servies implement web services:

• Using HTTP
• Compliant with RESTful constraints.

A RESTful web service must define:

1. Base URI (e.g. http://example.com/resources).
2. Supported data type (e.g. JSON, XML).
3. Supported operations using HTTP methods (e.g. GET, PUT, POST, or DELETE).
4. API that is hypertext driven.

• Wiki

• RESTful Web Services