[not_kurt_godel]

Deriving a presentation layer from an API definition has no bearing on whether the client has to be stateful or not. The key difference for 'true' HATEOAS is that the API schema is sufficiently descriptive that the client does not need to request any presentation layer; arguably not even HTML, but definitely not CSS or JavaScript.

https://ics.uci.edu/~fielding/pubs/dissertation/rest_arch_st...

> any concept that might be the target of an author's hypertext reference must fit within the definition of a resource

[alganet]

Dude, he literally mentions Java Applets as an example (it was popular back then, if it was written today it would have been JavaScript). It's all there. Section 5.1.7.

It's an optional constraint. It's valid for CSS, JavaScript and any kind of media type that is negotiable.

> resource: the intended conceptual target of a hypertext reference

> representation: HTML document, JPEG image

A resource is abstract. You always negotiate it, and receive a representation with a specific type. It's like an interface.

Therefore, `/style.css` is a resource. You can negotiate with clients if that resource is acceptable (using the Accept header).

"Presentation layer" is not even a concept for REST. You're trying to map framework-related ideas to REST, bumping into an impedance mismatch, and not realizing that the issue is in that mismatch, not REST itself.

REST is not responsible for people trying to make anemic APIs. They do it out of some sense of purity, but the demands do not come from HATEOAS. They come from other choices the designer made.

[not_kurt_godel]

I will concede the thrust of my argument probably does not fully align with Fielding's academic definition, so thank you for pointing me to that and explaining it a bit.

I'm realizing/remembering now that our internal working group's concept of HATEOAS was, apparently, much stricter to the point of being arguably divergent from Fielding's. For us "HATEOAS" became a flag in the ground for defining RESTful(ish) API schemas from which a user interface could be unambiguously derived and presented, in full with 100% functionality, with no HTML/CSS/JS, or at least only completely generic components and none specific to the particular schema.

[alganet]

It happens.

"Schema" is also foreign to REST. That is also a requirement coming from somewhere else.

You're probably coming from a post-GraphQL generation. They introduced this idea of sharing a schema, and influenced a lot of people. That is not, however, a requirement for REST.

State is the important thing. It's in the name, right? Hypermedia as the engine of application state. Not application schema.

It's much simpler than it seems. I can give a common example of a mistake:

GET /account/12345/balance <- Stateless, good (an ID represents the resource, unambiguous URI for that thing)

GET /my/balance <- Stateful, bad (depends on application knowing who's logged in)

In the second example, the concept of resource is being corrupted. It means something from some users, and something to others, depending on state.

In the first example, the hypermedia drives the state. It's in the link (but it can be on form data, or negotiation, for example, as long as it is stateless).

There is a little bit more to it, and it goes beyond URI design, but that's the gist of it.

It's really simple and not that academical as it seems.

Fielding's work is more a historical formalisation where he derives this notion from first principles. He kind of proves that this is a great style for networking architectures. If you read it, you understand how it can be performant, scalable, fast, etc, by principle. Most of the dissertation is just that.