Uniform interface

In REST principles, all resources are identified by the Uniform Resource Identifier (URI).

HTTP REST resources are represented in some media types, such as XML, JSON, and RDF. Also, RESTful resources are self-descriptive, which means enough information is given to describe how to process the request.

In another REST principle, the clients interact with servers through hypermedia, which is dynamically provided by the servers. Other than endpoints, clients don't need to know how to interact with RESTful services. This principle is referred to as Hypermedia as the Engine of Application State (HATEOAS).