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Re: aliasing elements

From: Al Gilman <Alfred.S.Gilman@IEEE.org>
Date: Thu, 17 Aug 2006 15:16:38 -0400
Message-Id: <p06110407c10a6a184a56@[]>
To: public-schemata-users@w3.org
Cc: Jim Jewett <jimjjewett@gmail.com>

At 3:00 PM -0600 8/16/06, C. M. Sperberg-McQueen wrote:
>On 16 Aug 2006, at 12:38 , Jim Jewett wrote:
>>Is there any way to alias an element or attribute from another namespace?
>Alas, not in the current state of the art.

[I speak as a fool.]

1. Machinable metadata in the schema

One, relatively indirect approach that we in the Protocols and
Formats Working Group have kicked around [1] as a possible approach to
documenting a compare-and-contrast with prior art [2] is to
use machinable metadata embedded in the xsd:appinfo in the schema.

Related to this is a debate (the jury still out so far as I know) as to
whether SKOS terms [3] are appropriate to apply to markup-language
concepts such as that represented in syntax by xml:id or xml:base.

But if one wanted to put a vanilla 'id' attribute in their own
namespace, could they, in RDF in xsd:appinfo, assert their intent
that it be processed the same as xml:id and that its values could not
overlap the values of the latter attribute in the appropriate scope?

[1] http://lists.w3.org/Archives/Public/wai-xtech/2005Oct/0010.html

[2] http://www.w3.org/TR/xag#cp4_5

[3] http://www.w3.org/TR/swbp-skos-core-guide/

2. Derivation

As I say, I am a fan of schemas, not an expert.

I thought that data structures are developed in two steps.  First the
structure is defined, and then bound to syntax.

Is this just for structures?  Or is the two-phase creation of typed
syntax global?

Can a new XML dialect import from a foreign schema at the type-definition
layer and bind to new and different syntax?  Does this fail in the case of
xml:id because the compromise struck over xml:id [4] does not depend on

[4]  http://www.w3.org/TR/xml-id/

3. Type sharing

Actually, for xml:id I don't see the problem. A dialect can declare
an attribute, whether named 'id' or anything else, to be of _type_ ID
and it is automatically a renames in that syntax of xml:id; so long
as the dialect supports the xml:id Rec at all. Because the uniqueness
rules are for "all values of attributes of type ID" and not "all
values of like-named attributes of type ID."

This, of course, makes "type=ID" a class, not a type, but it's what we need.

So I need another example, or an explanation of why that explanation does
not apply.


PS:  I speak as a fool...

>The idea has been kicked around, though, and it has seemed to
>some people that it would be convenient.  If it's something you
>would like to see in some future version of XML Schema, now would
>be a good time to say so.
>-C. M. Sperberg-McQueen
Received on Thursday, 17 August 2006 19:41:07 UTC

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