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Re: SVG schema: Relax NG or not?

From: Chris Lilley <chris@w3.org>
Date: Thu, 8 May 2003 16:18:33 +0200
Message-ID: <98229484765.20030508161833@w3.org>
To: Masayasu Ishikawa <mimasa@w3.org>
CC: www-svg@w3.org

On Thursday, May 8, 2003, 7:48:40 AM, Masayasu wrote:


MI> [ personal opinion ]

MI> Chris Lilley <chris@w3.org> wrote:

>> Comparing this RNG modularization to the DTD modularization though,
>> its also apparent how much cruft is simply not needed because the
>> namespace support in RNG is simple and elegant whereas the namespace
>> hacks that one uses in DTDs are a succession of flaming hoops to jump
>> though.

MI> Indeed.

>> TR> Perhaps Relax NG is a candidate format for the main SVG schema?
>> 
>> Yes; because then we can form XHTML2+SVG profiles with ease.

MI> That's part of the reason why I started to explore RELAX NG -
MI> an XHTML2+MathML+SVG schema can be as simple as this one:

MI>     http://www.w3.org/People/mimasa/test/schemas/rng/xhtml2-math-svg.rng

MI> Compare it with its DTD counterpart:

MI>     http://www.w3.org/TR/2002/WD-XHTMLplusMathMLplusSVG-20020809/#driver

MI> And most of the known limitations derived from DTD's inability to
MI> handle namespaces just go away:

MI>     http://www.w3.org/TR/2002/WD-XHTMLplusMathMLplusSVG-20020809/#bugs

MI> But frankly I don't expect everyone who wants to mix their own
MI> vocabulary with XHTML2 would move to RELAX NG, that's why the HTML
MI> WG plans to provide XHTML2 schemas in RELAX NG, XML Schema and DTD
MI> so that people can choose one that suits their needs.  Or better still,
MI> I personally hope that the Document Schema Definition Languages (DSDL)
MI> could eventually give us possibility to validate different "islands"
MI> with different kind of schema languages, e.g. RELAX NG for XHTML2 part
MI> and XML Schema for SVG part.

Or, more likely, RNG for the XHTML2 and SVG parts and XML Schema for
the mathML part (etc).

More interesting, RNG allows extensible type libraries, of which the
one that comes with W3C XML Schema is but one option.

Lots of W3C specs for example have types that cannot be described in
W3C XML Schema. Such as a 'length with unit". This is not terribly
complicated - width="3.5mm" - and there is clear BNF for the allowed
syntax.

It would be great to have a library for these sort of things - XSL,
SVG, SMIL could use it for example as could any future CSS-in-XML.

As an example, see
http://sourceforge.net/projects/relaxng
where there are COM, C++. .Net and Java implementations of type
libraries for RelaxNG.



-- 
 Chris                            mailto:chris@w3.org
Received on Thursday, 8 May 2003 19:11:08 GMT

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