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Re: Media types

From: Roy T. Fielding <fielding@ebuilt.com>
Date: Thu, 17 Jan 2002 15:18:13 -0800
To: Keith Moore <moore@cs.utk.edu>
Cc: "Simon St.Laurent" <simonstl@simonstl.com>, www-tag@w3.org, ietf-xml-mime@imc.org, mura034@attglobal.net
Message-ID: <20020117151813.A20009@waka.ebuilt.net>
On Thu, Jan 17, 2002 at 05:36:15PM -0500, Keith Moore wrote:
> > It would be difficult for such a thing to happen without the IETF, but
> > making changes to MIME of any fundamental sort is intensely difficult.
> > Despite the work I put into RFC 3023, and the very rough consensus we
> > managed to achieve there, I think XML is demonstrating the limitations
> > of MIME on a regular basis.
> that's a pretty bizarre statement.  perhaps it's truer to say that XML 
> is trying to misuse MIME on a regular basis?

Right.  I don't think XML is a media type, for the same reason that SGML
is not a media type.  [I know both are registered -- they are simply never
used correctly in the generic form.]

> or that expecting the MIME content-type to convey the action that 
> should be performed by a recipient, rather than a description of 
> the content, is a bit of a mis-application of MIME?

That's not always true. MIME uses the content-type to indicate what type
of handler should be selected for the message body.  The same content can
be sent for different purposes by using different media types. E.g.,
image/jpeg vs application/octet-stream, multipart/alternative vs
multipart/mixed, etc.  

> the fact that XML picked a means of labelling content that is
> incompatible with MIME's content-type is hardly MIME's fault.

I think the mistake is in assigning such messages a type that implies
it should be handled by a generic XML processor.  There is no such thing,
even though it is possible to view all XML types via generic XML tools.
A more architecturally fitting course of action would be to create a
top-level media type of xml and then have xml/* subtypes, but for
some reason (deployed apps, I presume) the top-level namespace has been
frozen for ages.

Received on Thursday, 17 January 2002 18:23:42 UTC

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