Define a media type for annotation sets

[llemeurfr]

This specification introduces a dedicated media type value to identify an AnnotationSet: application/rd-annotations+json.

I propose using a “rd-” prefix (for ReaDium). It would allow for easier registration at IANA.

Is it a good idea?
Should we extend this to other media types, including “application/webpub+json”?

[HadrienGardeur]

This feels like a halfway point between media types in the vendor tree (application/vnd-*) and standard tree (let's say application/pdf).

For any standard that we'd like to push to a standard body recognized by IANA, it's best to target the standard tree. For anything that should remain vendor-specific, it's best to use the vendor tree.

[llemeurfr]

This is a generic take. Now look at the IANA registry, there are sets of values prefixed by "alf+", "alto-", 'atsc-", "cdmi-" ... These prefixes represent families.