A client's request and server's response are messages; those messages should be stateless and self-descriptive. They can have a body and metadata. RESTful applications operate on the notion of constrained message types (GET, HEAD, OPTIONS, PUT, POST, and DELETE) and they are fully understood by both the server and the client.
A resource's desired state can be represented within a client's request message. A resource's current state may be embodied within the response message that comes back from a server. As an example, a wiki page editor client may use a request message to transfer a representation that suggests a page update (new state) for a server-managed web page (resource). It is up to the server to accept ...
