W3C home > Mailing lists > Public > xml-uri@w3.org > May 2000

Re: Why are relative NS identifiers used?

From: John Cowan <jcowan@reutershealth.com>
Date: Fri, 19 May 2000 09:30:06 -0400
Message-ID: <392541DE.C35073C3@reutershealth.com>
To: Rick JELLIFFE <ricko@geotempo.com>, "xml-uri@w3.org" <xml-uri@w3.org>
Rick JELLIFFE wrote:

> Nor will it work to keep on avoiding this issue: if Tim BL thinks the
> architecture
> of the WWW should involve directly dereferencing namespace identifiers
> to
> get schemas, then he should put it up as a formal proposition and either
> get it voted
> on by W3C or declare it by fiat for W3C technology.

Not necessarily.  For example, it might be in order to look up the namespace
(by its URI) in an RDF database and determine its "xmlSchema" property.
That can't be done unless the namespace is a resource named by a true URI,
because RDF is about properties of resources.

Whether a namespace name is a URI reference or not is separable from the
question of direct dereference.

>  1) A revision of the namespace wRECk to add a mechanism where W3C WGs can
> define well-known relative URIs which, when appended to the NS identifier,
> give standard locations for various kinds of schemas and information. For
> example, to find schemas and DTDs, RDF schemas, default stylesheets, WAI-specific
> stylesheets, editing tools, etc.  Each WG should define the appropriate
> well-known relative URL for locating the kinds of resources they deal in,
> relative to a NS identifier: for example, the HTML WG could specify various
> locations for the various DTDs and schemas and WAI schemas for XHTML, the
> NS URI for HTML being the root for these.

This is overly clunky compared to using RDF directly; it amounts to RDF
declarations that say:

	<rdf:Description about="http://www.example/ns/foo.html">
		<stylesheet resource="http://www.example/ns/sheets/foo.css">
		<schema resource="http://www.example/ns/schemas/foo.xschema">
		etc. etc.
	</rdf:Description>

or the like.  Clearly it is better to have a way of spelling these relationships
out explicitly.  (*Finding* the RDF database that describes them is a separate
problem, but at least it's only a single problem, and uses a properly
extensible scheme.)

> We can specify different
> DTDs (thanks to SGML) and different stylesheets (thanks to James Clark)
> but can we specify anything else (except privately)?

Yes. With RDF (including embedded RDF) we can specify any document properties
our little hearts desire.
 
-- 

Schlingt dreifach einen Kreis um dies! || John Cowan <jcowan@reutershealth.com>
Schliesst euer Aug vor heiliger Schau,  || http://www.reutershealth.com
Denn er genoss vom Honig-Tau,           || http://www.ccil.org/~cowan
Und trank die Milch vom Paradies.            -- Coleridge (tr. Politzer)
Received on Friday, 19 May 2000 09:30:25 UTC

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