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Re: Registration of media type image/svg+xml

From: Chris Lilley <chris@w3.org>
Date: Tue, 20 Dec 2005 15:41:53 +0100
Message-ID: <1644306611.20051220154153@w3.org>
To: Bjoern Hoehrmann <derhoermi@gmx.net>
Cc: ietf-types@iana.org, www-tag@w3.org

On Saturday, December 17, 2005, 12:35:12 AM, Bjoern wrote:

BH> * Chris Lilley wrote:
>>With RFC 3023 as it stands, however, it has all the problems that the
>>TAG finding notes regarding inconsistency of dual metadata; in
>>consequence it was felt safer to omit the parameter. As RFC 3066
>>carefully describes a consistent handling of +xml media types where a
>>charset is omitted, this was not felt to be a problem.

BH> The idea of RFC 3023's +xml convention is that applications can consider
BH> resources labeled with such types XML and process them in a generic way
BH> even if the specific media type is not known to the application.

Yes, I am familiar with the concept.

BH> This is not guranteed if the rules for detecing the character
BH> encoding of image/ svg+xml resources are different from those for
BH> application/xml resources or other non-text/* +xml types.

They aren't. As the registration says,

      This has identical semantics to the application/xml media type in
      the case where the charset parameter is omitted, as specified in
      RFC3023 sections 8.9, 8.10 and 8.11.

Thus, any content labelled at image/svg+xml can be treated as
application/xml and its encoding reliably determined according to the
rules given in RFC 3023.

BH> If you want to say that the charset parameter is better not used for
BH> image/svg+xml resouces that's fine,

"Better not used" is wooly, and conflicts with RFC 3023 which STRONGLY
RECOMMENDS that it be used at all times. Thus, the only safe way was to
omit it altogether.

BH> defining or implying different
BH> encoding detection requirements for image/svg+xml resouces than what
BH> we have for application/xml is not, as that would make the types
BH> incompatible.

Its not different; its a subset.

Now, a revision of RFC 3023 that said what the TAG finding says, would
make this a lot less dangerous and adding a charset parameter might then
be possible.

 Chris Lilley                    mailto:chris@w3.org
 Chair, W3C SVG Working Group
 W3C Graphics Activity Lead
 Co-Chair, W3C Hypertext CG
Received on Tuesday, 20 December 2005 14:42:00 UTC

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