Re: [media-types] Media subtypes containing "+"

["Martin J. Dürst" <[e-mail]>]

On 24/12/2020 07:35, Murray S. Kucherawy wrote:
> Hi Amy, sorry for the delay.  Thanks for taking this on.
> 
> A question and a suggestion:
> 
> (1) In terms of handling, you might also propose this to [e-mail] (the
> general ART area mailing list) and to [e-mail] (the DISPATCH
> working group); the latter would be the place to get a discussion going
> about an appropriate venue for handling the document.
> 
> (2) I'm unclear on the nomenclature, in particular that the most specific
> suffix is the first in the list of suffixes (when read left to right) and
> the most generic is last.  My thought is that the list needs to be ordered,
> and we just need to specify what that ordering is.  For instance, I'm
> dreaming up a (possibly absurd) example of "foo+zip+gzip".  Would I un-gzip
> it first, or unzip it first, with the goal of getting a "foo" out of it?
> Why would I consider one of them more specific or generic than the other?

If I understand correctly, you would un-gzip it first, and only then 
unzip it. In a slightly more realistic example, let's use svg+xml+gzip. 
Gzip is more generic (because it can be applied to any kind of data) 
than xml, and you definitely first have to un-gzip before feeding the 
document into an XML parser.

But you may be right that there are cases where the terminology 
'generic'/'specific' may not be adequate. foo+gzip+zip (foo gzipped and 
then zipped) may make as much (or as little!) sense as foo+zip+gzip,


> If (based on the end of Section 1.1) what you're suggesting is actually to
> in effect consider "+zip+gzip" a single unified suffix of its own, then I
> think what we're really saying here is that there's only ever one suffix,
> but that suffix can contain a "+".  That is, when parsing the media
> subtype, the suffix is everything at and after the first "+" irrespective
> of how many "+" characters there are.  If that's the case, it might be
> simpler to just say it that way so that the reader doesn't need to think
> about a gradation of most-to-least specific.

The problem with this approach may be that currently existing 
implementations, as well as some future implementations, may just look 
at the rightmost + and the following alphabetic characters. Therefore, 
you need to make sure that people constructing/proposing suffix 
combinations will choose the right order, and that means that you have 
to have some language about suffix ordering anyway.

Regards,   Martin.


> -MSK
> 
> On Mon, Nov 30, 2020 at 6:49 AM rhiaro <[e-mail]> wrote:
> 
>> Hi all,
>>
>> As requested, we have a draft which is an update to RFC 6838, so that we
>> can discuss something concrete around multiple subtype suffixes:
>>
>>
>> https://datatracker.ietf.org/doc/draft-w3cdidwg-media-types-with-multiple-suffixes/
>>
>> Does anybody have a few moments to review this, so we can work on moving
>> this forward?
>>
>> Many thanks,
>>
>> Amy