What are the standards for being considered restful?

The main aspects of RESTful specifications include:

1. Use Uniform Resource Identifiers (URI) to identify resources. URIs should be meaningful, easy to read, and able to clearly describe the resource.
2. Resources can be manipulated using HTTP methods. These methods include GET, POST, PUT, DELETE. GET is used to retrieve resources, POST is used to create resources, PUT is used to update resources, and DELETE is used to delete resources.
3. HTTP status codes are used to indicate the results of a request. Common status codes include 200 for success, 201 for successful creation, 204 for no content, 400 for a request error, 404 for a resource not found, and 500 for a server error.
4. Extra information can be passed using HTTP request headers. Common HTTP request headers include Accept, which indicates the response types the client can accept, Content-Type, which indicates the type of data in the request body, and Authorization, which represents authorization information.
5. HTTP response headers are used to convey additional information. Common HTTP response headers include Location for indicating the location of a resource, Cache-Control for specifying caching strategies, and Allow for listing allowed HTTP methods.
6. Handle errors by using appropriate HTTP status codes and error messages. When an error occurs, return the appropriate HTTP status code and provide detailed error information to assist the client in handling it.
7. Implementing hypermedia-driven APIs using the HATEOAS principle involves including links between resources in responses, allowing clients to dynamically access related resources through these links. This reduces the coupling between clients and servers, enhancing the flexibility and scalability of the API.

In general, the RESTful specification primarily defines and operates resources using URI, HTTP methods, HTTP status codes, HTTP request and response headers, and implements hypermedia-driven APIs through the HATEOAS principle.