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Re: More thoughts on 'Client handling of MIME headers'

From: Ian B. Jacobs <ij@w3.org>
Date: 14 Jul 2003 18:03:54 -0700
To: Chris Lilley <chris@w3.org>
Cc: WWW-Tag <www-tag@w3.org>
Message-Id: <1058231034.903.150.camel@seabright>

Hi Chris,

This comment makes sense and I will make appropriate editorial
changes.

 _ Ian

On Mon, 2003-07-14 at 11:34, Chris Lilley wrote:
> Hello WWW-Tag,
> 
> >> Another benefit of separating metadata that guides interpretation
> >> from data is improved efficiency. For instance, when a server sends
> >> XML data and labels the data correctly through MIME headers, a
> >> client can dispatch processing after rapid inspection of the
> >> metadata (typically short strings). It is much more expensive if
> >> the client has to start up an XML parser to guess the content type.
> http://www.w3.org/2001/tag/doc/mime-respect.html
> 
> Its not clear that this assertion is true.
> 
> So I send some xml data labelled as application/xml and it contains a
> bunch of xml namespaces (but I am not going to tell you what they are
> or what the rootmost one is, because you need to parse the xml to get
> that information). Similarly, peeking in the xml and noticing that
> there is a PI to link to a stylesheet is also not allowed here. So
> what can really be done?
> 
> So, starting an xml parser (or attaching to an existing one) should
> not be needed for 'guessing the content type', true, but may well be
> needed to decide on appropriate processing.
> 
> I certainly agree that startiong a parser to see if it is xml would be
> a bad thing.
> 
> The trouble in the text above is that it goes straight from
> 'determining content type' to ' dispatch processing' while assuming
> the latter is an atomic, single step process.
> 
> So I would agree that correct labelling allows the first step to be
> dispatching to be done automatically; the current text seems to
> suggest that there can only be one step, and there I disagree. Given a
> firm identification of content as application/xml, parsing the content
> is a likely and reasonable second step and the finding should take
> care not to inadvertently suggest otherwise.
-- 
Ian Jacobs (ij@w3.org)   http://www.w3.org/People/Jacobs
Tel:                     +1 718 260-9447
Received on Monday, 14 July 2003 21:03:55 GMT

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