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RE: XML validity and namespaces

From: Paul Cotton <pcotton@microsoft.com>
Date: Sun, 3 Apr 2005 12:03:38 -0700
Message-ID: <33D970235519324D988AFFDE7EA2E24C056F869A@RED-MSG-41.redmond.corp.microsoft.com>
To: "Rich Salz" <rsalz@datapower.com>
Cc: <www-tag@w3.org>

> XML validity is important, and perhaps should be separated from DTD's.

Have you asked this question of the W3C XML Core WG?  If the answer is
yes can you provide a pointer to your dialogue with them?

If not, shouldn't you start with the XML Core WG instead of the TAG
since the XML Core WG is responsible for maintenance of the XML


Paul Cotton, Microsoft Canada 
17 Eleanor Drive, Nepean, Ontario K2E 6A3 
Tel: (613) 225-5445 Fax: (425) 936-7329 


> -----Original Message-----
> From: www-tag-request@w3.org [mailto:www-tag-request@w3.org] On Behalf
> Rich Salz
> Sent: April 3, 2005 2:25 PM
> To: www-tag@w3.org
> Subject: XML validity and namespaces
> DTD's are ignorant of namespaces.  This means that you cannot write a
> normative DTD for a namespace (as you might do with XML Schema). The
> best you can hope to do is write something for expository purposes,
> using particular namespace prefixes as an example.  Each instance of
> a document would then have to rewrite the DTD to use the namespace
> prefixes that are used in the document.
> If the document uses elements from multiple namespaces, however,
> and even if you can collect all the DTD's and rewrite them to map
> the prefixes used in a particular document instance, you can't do
> this for every case.  Viz:
>     <tns:Foo xmlns:tns="http://example.com/1999">
>         <tns:Foo xmlns:tns="http://example.com/2002">
>             content
>         </tns:Foo>
>     </tns:Foo>
> It seems to me, then, that DTDs are not useful, and maybe not
> even possible, for XML standards or documents that use namespaces.
> The problem with this is that XML validity requires a DTD (see [1]).
> XML Schema, in a round-about way, enforces ID attribute uniqueness,
> but only for that part of the document that is being validated;
> if the schema does not start at the document root, there is no
> guarantee.  The desire for composability means comparatively few
> schemas (at least horizontal ones, such as developed by standards
> organizations) will cover the entire document.  XML Schema may
> also enforce other aspects of XML validity; I am not familiar enough
> with the specs to say.
> XML validity is important, and perhaps should be separated from DTD's.
>         /r$
> [1] http://www.w3.org/TR/2004/REC-xml-20040204/#dt-valid
> --
> Rich Salz                  Chief Security Architect
> DataPower Technology       http://www.datapower.com
> XS40 XML Security Gateway  http://www.datapower.com/products/xs40.html
Received on Sunday, 3 April 2005 19:03:46 UTC

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