[media-types] Thoughts on suffixes, single and multiple

[Darrel Miller <[e-mail]>]

As a follow up to the tests that I did to see if any of the major browsers respect +json, which they didn't, I tried the same experiment with +xml and got the same results.  None of the browsers I tried, used the +xml suffix to cause XML rendering.

This leads me to feel like that we are debating over what is theoretically possible, but in the 23 years since suffixes were formalized, that theoretical value has not been widely realized. We do not have a clear guidance on what the suffix means.  For example,  +json and +gzip are achieving quite distinct goals. We have seen that introducing multiple suffixes has raised a range of new concerns that we do not have clear answers for.

Most of the proposed uses of single and multiple suffixes that I have seen are either trying provide an encoding format that overlaps with Content-Encoding, or they are being used as a indicator to client or server of the specific format of some content where multiple contents are supported.

An example of the latter scenario is what we have been trying to do with the registration of the media type for OpenAPI descriptions https://www.ietf.org/archive/id/draft-ietf-httpapi-rest-api-mediatypes-05.html#section-2.1

The proposal is to register application/openapi+yaml and application/openapi+json.  This allows clients to conneg the format they desire and servers to advertise the format they are returning.

However, upon reflection of all this conversation around suffixes, my question is why not do this?

application/openapi;format=yaml
application/openapi;format=json

By defining an optional format parameter for the media type, we only have to have one registration, we get the same value and a client has the option to omit the format if either is supported.

John Klensin made the comment in one of the recent IETF mediaman meetings that parameters for media types were created to prevent there being an explosion of media type registrations.

Is there a reason why media type parameters cannot be used in many of these other use cases that are currently struggle to shoehorn information into suffixes?

e.g.
application/vc;format=jsonld
application/did;format=jsonld
application/voucher;format=json;sig=jose
application/voucher;format=cbor;sig=cose


I think suffixes were an experiment into encoding some meaning into part of a media type name that did not produce the desired results. I don't believe that if we decided to remove that meaning that anything on the internet will break.  Existing suffixes can remain, but I think moving forward we should be looking towards leveraging parameters, not suffixes for capturing meta information about media types.

Darrel