Representational state transfer (REST) is a software architectural style that defines a set of constraints to be used for creating Web services. Web services that conform to the REST architectural style, called RESTful Web services (RWS), provide interoperability between computer systems on the Internet. RESTful Web services allow the requesting systems to access and manipulate textual representations of Web resources by using a uniform and predefined set of stateless operations. Other kinds of Web services, such as SOAP Web services, expose their own arbitrary sets of operations.
For those that, at some point, need to test what means that of ECP for horizontal escalability (computing power and/or users and processes concurrency), but they're lazy o have no much time to build the environment, configure the server nodes, etc..., I've just published in Open Exchange the app/sample OPNEx-ECP Deployment .