I know, even though that depends on the editor. Okular for example places them in an extra file, last I checked. That's not unique to PDFs. HTML files are modifiable. There is nothing preventing an editor to put annotations in it as well.
It definitely used to be bizarre then:
https://superuser.com/questions/333378/where-does-okular-sto...
turns out the default for okular is to save to an external file but there's a setting that can be changed to use the format correctly and store annotations within the file, which is universally compatible with other PDF readers. You can't really blame the format for someone using it wrong on purpose, and if you can then I'll just abuse HTML and the fact that I use it wrong will be evidence that it is, in itself, wrong
That's different. Those are a data structure defining annotations that are meant to be stored externally. They're not part of an HTML file like PDF annotations are. They're meant more for live collaborative commenting within a shared online space, not for making private portable annotations like PDF does.
And it's not a Chrome thing. I don't think any browsers support it, do they? It's not really clear there's a need for it, when collaborative editors already handle document annotations in their own ways.
So is there a need for it or isn't there?
> That's different. Those are a data structure defining annotations that are meant to be stored externally.
The protocol is a separate standard.
The format is JSON-LD. Putting JSON-LD into HTML isn't a question mark. (There's info at W3C.org about how to do that, too. Not that it's necessary. You can guess what it says.)
PDF is designed for annotations in the file format. You annotate in one editor, you can change the annotations in another. You can always distinguish between original content and annotations. I see no indication that Okular stores highlights or annotations in a separate file, that would be bizarre.
There is no mechanism for annotations in HTML or the other formats I listed. An editor would just be editing the original content in its own non-standardized, non-portable way, which is not desirable for a number of reasons.
So when you say:
> What you are describing are features of an editor, not a file format.
That is incorrect. It is an intentionally designed and standardized feature of the file format.