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Re: XLink: the architectural issue

From: Eric van der Vlist <vdv@dyomedea.com>
Date: 27 Sep 2002 08:59:11 +0200
To: Steven Pemberton <steven.pemberton@cwi.nl>
Cc: www-tag@w3.org, HTML WG <w3c-html-wg@w3.org>
Message-Id: <1033109952.25579.814.camel@ibook>

On Fri, 2002-09-27 at 01:34, Steven Pemberton wrote:

<good_and_simple_stuff_sniped/>

> However, if some specification, say XDates, appropriates all attributes of
> type Date, then you can't just do this, you have to look to see what other
> attributes are already in use. So instead of
> 
>     <para abc:created="2001-01-01" xyz:edited="2002-09-26">
>         Now is the time
>     </para>
> 
> I would have to say
> 
>     <para>
>         <created xdate:date="2001-01-01"/>
>         <edited xdate:date="2002-09-26"/>
>         Now is the time.
>     </para>

That's a great way to present the problem and show it as a consequence
of the lack of extensibility of XML attributes.

I'd like to make a (probably silly) proposal for a novel usage of
namespaces. Of course, it wouldn't apply to XLink which is already baked
and a generic schema for the xdate namespace wouldn't be possible to
express with W3C XML Schema (too bad, you'd have to use Relax NG :-) )
but if we said that the xdate namespace is identifying dates and that
"host vocabularies" may choose any local name in this namespace to
express their dates, we could write:

<para xdate:created="2001-01-01" xdate:edited="2002-09-26">
	Now is the time
</para>

The xdate namespace would identify the nature of the attribute and its
local name would identify its purpose as defined by the host vocabulary.
It's probably not ideal, but when we play with attributes, we don't have
that much variables we can play with!

The other (quite ugly IMO) solution would be through the PSVI (don't
care what the local name and namespace of the attribute are but its type
must be xdate:date) but it would make the usage of W3C XML Schema
mandatory and I see HLink as a lightweight alternative to achieve the
same kind of functionality.

Eric
-- 
Rendez-vous  Paris.
                          http://www.technoforum.fr/integ2002/index.html
------------------------------------------------------------------------
Eric van der Vlist       http://xmlfr.org            http://dyomedea.com
(W3C) XML Schema ISBN:0-596-00252-1 http://oreilly.com/catalog/xmlschema
------------------------------------------------------------------------
Received on Friday, 27 September 2002 02:59:45 GMT

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