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Re: XPointer considered incomprehensible

From: <noah_mendelsohn@us.ibm.com>
Date: Tue, 5 Sep 2006 10:02:35 -0400
To: Bjoern Hoehrmann <derhoermi@gmx.net>
Cc: "Jonathan Marsh" <jmarsh@microsoft.com>, www-tag@w3.org, www-xml-linking-comments@w3.org
Message-ID: <OF40B199D1.AADBC7EF-ON852571E0.004C5A9B-852571E0.004D25D0@lotus.com>

Bjoern Hoehrmann writes:

> We currently do not have a sound architecture built around the many
> XML media types. We do not have specifications that address cases
> like the one you cite - SVG content labeled application/xml - in any
> way. My understanding is that web browsers tend to consider all the
> XML media types (*/xml and */*+xml) exactly the same. There isn't
> much wrong with that so long as they actually are the same, but at
> least in case of fragment identifiers, they are not.
> 
> I recently researched the registered +xml media types for what their
> specifications say about fragment identifiers and found that only
> three type make an attempt to say something about the matter by them-
> self:
> 
>   * application/xhtml+xml       -> Probably ID references
>   * application/smil+xml        -> as above plus maybe XPointer
>   * application/rdf+xml         -> I don't understand the RFC
> 
> Then there are two types that refer to application/xhtml+xml, nine
> types that refer to application/xml, and the other 57 types do not
> define their fragment identifier syntax, if any. My understanding is
> that some people propose application/xml should allow for any and all
> XPointer schemes; if we do that, it would become, in a way, the super-
> type for all XML media types, whereas people currently tend to think
> of it as a base type.

I note that RFC 3023 [1] says of xxxx+xml media types:

"This document recommends the use of a naming convention (a suffix of 
'+xml') for identifying XML-based MIME media types, whatever their 
particular content may represent.  This allows the use of generic XML 
processors and technologies on a wide variety of different XML document 
types at a minimum cost, using existing frameworks for media type 
registration.

[...]

Some areas where 'generic' processing is useful include:

   o  Browsing - An XML browser can display any XML document with a
      provided [CSS] or [XSLT] style sheet, whatever the vocabulary of
      that document.

   o  Editing - Any XML editor can read, modify, and save any XML
      document.

   o  Fragment identification - XPointers (work in progress) can work
      with any XML document, whatever vocabulary it uses and whether or
      not it uses XPointer for its own fragment identification."

So, the architecture seems to be:  XPointer must be usable with any of the 
+xml family.  There is at least a hint that the specific xxxx+xml media 
type need not use XPointer for its own fragment identification.  This 
seems a bit strange to me, but it obviously was carefully considered when 
3023 was drafted.

Noah

[1] http://www.rfc-archive.org/getrfc.php?rfc=3023

--------------------------------------
Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142
1-617-693-4036
--------------------------------------
Received on Tuesday, 5 September 2006 14:03:02 GMT

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