If you're going to get that picky (and please be aware I'm only doing this for the sake of the argument) media can never be hypermedia in the absence of the client. HTML opened in notepad is just text. Cat GIFs, rendered in the correct client, would absolutely be hypermedia (you could inline link data as QR codes, if you felt like being perverse).
Hypermedia starts with the client, not with the file format.
I agree that a hypermedia can't act properly within the uniform interface constraint, without a hypermedia client, that is, you can't have a hypermedia system without a proper hypermedia client:
On the other hand, there is a real difference between plain text and HTML (or HXML, don't shoot!) which is a subset of text with additional concepts layered on top of it. This is akin to how JSON (or XML) is not hypermedia, but can be used to create hypermedia such as Siren or HXML.
So I still think it makes sense to discuss if a media is or is not hypermedia without reference to the client, whereas it doesn't make sense to claim it is being used as hypermedia unless it is being consumed by a properly written hypermedia client. To make my thinking concrete, I believe Siren would continue to be hypermedia, even if it wasn't be consumed properly by a client, but then also you could not describe that pairing as a hypermedia system. (This is one reason I focus on the systemic nature of hypermedia, rather than solely on hypermedia formats)
Semantic nitpicking perhaps, but then hypermedia discussions appear to tend to invite this sort of thing.
> HTML (or HXML, don't shoot!) which is a subset of text with additional concepts layered on top of it. This is akin to how JSON (or XML) is not hypermedia
So, HTML is different from plain text because it "has concepts layered on top of text" where as JSON is not hypermedia despite "having concepts layered on top of text". And the only reason is because you said so.
> So I still think it makes sense to discuss if a media is or is not hypermedia without reference to the client
Then JSON is just as much hypermedia as HTML. Both are structured text unusable without a specific client to display them or work with them.
> Semantic nitpicking perhaps, but then hypermedia discussions appear to tend to invite this sort of thing.
They only invite them because of your insistence on calling only HTML the "natural hypermedia" etc.
No, the reason is because HTML qua HTML has hypermedia controls and JSON qua JSON does not. Recall that, before I pointed out the widely used and accepted definition of hypermedia controls, and in particular that links and forms are hypermedia controls, you did not understand that concept, so you might spend some time quietly reflecting on that idea. It may help clarify things for you.
> Then JSON is just as much hypermedia as HTML. Both are structured text unusable without a specific client to display them or work with them.
As I have said and written previously (https://htmx.org/essays/hypermedia-clients/, https://hypermedia.systems/hypermedia-components/) I agree that a hypermedia client is necessary for a properly functioning hypermedia system that adheres to the uniform interface. However, I think that there is a good argument that Siren, for example, is hypermedia, even if it isn't being consumed correctly, just as I think HTML is hypermedia, even if someone is screen scraping it (i.e. not using a hypermedia client to consume it).
I don't think you can call those uses a hypermedia system, but I also don't think that changes the fact that the underlying formats, Siren & HTML, are hypermedia, due to the fact that they have hypermedia controls. That might be a subtle distinction, but I think it is a valid one. Again, perhaps as you reflect more on this concept, new to you, of hypermedia controls, the distinction will become easier to understand.
> They only invite them because of your insistence on calling only HTML the "natural hypermedia" etc.
I'm very sorry you that feel that way.
I would call HTML, "a natural hypermedia", rather than "the natural hypermedia". I would also call HXML & Siren natural hypermedia, due to the presence of hypermedia controls (a concept new to you) in their specifications.
As such, they're ancillary sub-resources to hypermedia but not themselves hypermedia.