Resources in REST

• Client consumes servers capability by interacting with resources
• Resources are identified by a resource identifier.In http terms this is an URL
• Client interacts with resources the client does not work directly with the resources but with representations of those resources

         Example Person can be identified by name. We directly do not work with the Person by representation of person using JSON or XML. The message should also contain meta data about what to do with the services

HATEOAS on REST

HATEOAS, an abbreviation for Hypermedia As The Engine Of Application State, is a constraint of the REST application architecture that distinguishes it from most other network application architectures. The principle is that a client interacts with a network application entirely through hypermedia provided dynamically by application servers. A REST client needs no prior knowledge about how to interact with any particular application or server beyond a generic understanding of hypermedia. By contrast, in some service-oriented architectures (SOA), clients and servers interact through a fixed interface shared through documentation or an interface description language (IDL).

The HATEOAS constraint decouples client and server in a way that allows the server functionality to evolve independently.