Re: MPEG asks for MIME review for the MPEG21 file format

Graham Klyne <GK@ninebynine.org> Mon, 21 May 2007 09:14 UTC

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Date: Mon, 21 May 2007 10:13:58 +0100
From: Graham Klyne <GK@ninebynine.org>
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To: Chris Lilley <chris@w3.org>
CC: Dave Singer <singer@apple.com>, Martin Duerst <duerst@it.aoyama.ac.jp>, Anne van Kesteren <annevk@opera.com>, Larry Masinter <LMM@acm.org>, ned.freed@mrochek.com, ietf-liaisons@ietf.org, "'Christian Timmerer (ITEC)'" <christian.timmerer@itec.uni-klu.ac.at>, ietf-types@alvestrand.no, ietf-xml-mime@imc.org
Subject: Re: MPEG asks for MIME review for the MPEG21 file format
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Chris Lilley wrote:
> On Friday, May 18, 2007, 5:27:52 PM, Dave wrote:
> 
> (I'm snipping the parts already covered by Martin)
> 
> DS> Is a ZIP compressed XML file servable under a +xml MIME type? 
> DS> "encoding='zipped Shift_JIS'"?
> 
> I suspect you mean gzip, which is a compression method; zip is an archive format (often compressed internally).
> 
> If you started with foo.xml in Shift_JIS, the encoding declaration would say just that. If you then make foo.xml.gz the encoding declaration (when decompressed) says exactly the same thing. The fact that is been gzipped is conveyed out of band, in the http headers:
> 
> Content-Encoding: gzip
> 
> There is scope for confusion, since XML uses 'encoding' for 'character encoding' (although that's a big advance on calling it 'charset'). HTTP uses content-encoding. The two uses of the concept 'encoding' occur at different levels in the stack.
> 
> In consequence, using gzip content-encoding is compatible with +xml media types.

For clarification: this would be the case only when a suitable MIME
content-transfer-encoding header is applied, n'est pas?  Otherwise such added
encoding/decoding could be applied lower in the stack and not visible at the
level of the MIME object.

#g

-- 
Graham Klyne
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