Hypermedia as the Engine of Application State (HATEOAS) is one of the most critical constraints; without addressing it, services cannot be termed RESTful services. However, before we get into the details of HATEOAS, let's get a brief idea about the Richardson Maturity Model (RMM) as it is an essential reference and serves as a guide to any RESTful services to follow the HATEOAS constraints.
The RMM is a model developed by Leonard Richardson, and it breaks down the principal elements of the REST approach to Resources, HTTP Verbs, and Hypermedia Controls. The following diagram depicts the RMM's four levels, and those levels are used to grade the APIs; that is, the better the API adheres to these ...
