Chapter 1 Hypermedia Types

It is generally understood that, in the REST architectural style, “hypermedia is the engine of application state”[8]. But what does that really mean? What is hypermedia? Can it be identified within a resource representation? How can hypermedia be the “engine of application state?” In this chapter, a number of different notions of ”hypermedia” along with a formal definition of “Hypermedia Type” will be presented. In addition, nine Hypermedia Factors (H-Factors) that can be found in resource representations are identified and examples of these factors are provided. Armed with these nine H-Factors, several registered media types are analyzed to determine the presence of these hypermedia elements and to quantify the hypermedia support native to these media types. Finally, a prototypical media type (PHACTOR) is defined and reviewed in order to show how H-Factors can be incorporated into a media type in order to produce a data format that can act as an engine of application state.