Richardson Maturity Model
Up to this point we have discussed REST is a very broad sense. There are however specific guidelines associated with properly implementing RESTful protocols.
Leonard Richardson developed a model that divides the principles of REST into 3 steps. You can view them here. These can be used to grade your API according to the constraints of REST.
The glory of REST¶
0: Swamp of POX¶
Level 0
* Tunnels the request and response through its protocol without using the protocol to indicate application state. It will use only one entry point (URI) and one kind of method (typically POST). —> e.g. SOAP
1: Resources¶
Level 1
* API can distinguish between different resources. Uses multiple URIs, each URI is the entry point to a specific resource. Indicates specific resources with id: (e.g. example.org/products, example.org/products/1) -> Still only uses (GET/POST)
2: HTTP Verbs¶
Level 2 * Uses protocol properties in order to deal with scalability and failures (i.e. Status). Uses correct verbs for correct process (GET/PUT/POST/DELETE). Strong separation between safe GET and unsafe modification verbs.
3: HyperMedia Controls¶
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HATEOAS (HyperText As The Engine Of Application State). Introduces the concept of a self-documenting resource. The response to a request will include information about how to interact with the resource - i.e. additional URIs that can be accessed, and the relative links they should be appended to. For example:
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{linkRel : "/doctors/mjones", uri : "/slots/1234/appointment"}which would request the appointment document for a specific doctor at a specific slot.