xml-dev - Re: an unfilled need

["Martin Bryan" <mtbryan@sgml.u-net.com>]

Rick Jeliffe wrote
> I note Ann Navarro's call for "An unfulfilled need" earlier this month,
on a subject I also have been calling for for 2 years+: the need for a
mechanism to bind information to names: "definitions, semantics, and
other data that may be necessary to complete their operations."    This
looks to me like a case of two non-commercial voices being lost to more
important voices.

This view has also been expressed by The XML/EDI Group, and the recently
formed CEN/ISSS Defining and Managing Semantics and Datatypes project team,
but in this case they have been discussing them in terms of the semantics of
electronic commerce.

>I wonder if the reason can be found in Tim B-Ls recent post:

> Rick Jelliffe:
>>There is no W3C method to declare which schema should be
>>used, akin to the stylesheet declaration.

> Yes there is: resolution of the schema URI.

>Tim is saying that using the namespace URI to specify a schema
is the official W3C method. But there is nothing about this in
any W3C spec; no working group has decided this or put it out
in a public draft or spec.

>On the contrary "It is not a goal that it [the namespace URI] be
directly usable for retrieval of a schema (if any exists)"  says
XML NS.

>That is a major architectural decision implied on top of namespaces;
the only parties I see that can benefit from hardcoding schema
URIs into namespace URIs are vendors, who could use this
mechanism and only provide schemas in languages which they
controlled or provided tools for: I don't think this is far-fetched--
Biztalk mandates XDR schemas only.

One of the techniques the XML/EDI community have been propounding is the use
of namespaced attributes to point to semantic specifications using the XLink
mechanism or an application specific mechanism. Basically the namespace of
the attribute points to the rules for interpreting the attribute value and
the value of the attribute points to the definition of the semantics that
are to be applied to the element. This way you do not need to rely on the
namespacing of the element name - you simply indirect your element name into
the name space of the semantics definer. Using this technique you can
decouple the model language used for the message from any model associated
with the semantics. This means that it does not matter how the semantics
have been defined (XML-Data, RDF, text, etc) you can still use a DTD or a
Schema to model your message. To me this gets over the problems that would
arise if W3C tried to define formal mechanisms for the linking of namespace
URIs to schemas, etc.

Martin Bryan

Warning: As I only have time to look at the weekly XML-DEV archive, and will
be out of the country for the rest of this week, I may not reply in a timely
function to any reactions to this message.


-----------------------------------------------------------------

Martin Bryan, 29 Oldbury Orchard, Churchdown, Glos GL3 2PU, UK
Phone/Fax: +44 1452 714029 E-mail: mtbryan@sgml.u-net.com
For more information about The SGML Centre contact
http://www.sgml.u-net.com
For more information about the European Commission's
Open Information Interchange (OII) initiative contact
http://www.echo.lu/oii/en/oiistand.html
For more information about the ISIS XML/EDI Project contact
 http://wwe.tieke.fi/isis-xmedil.html


xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@ic.ac.uk
Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ and on CD-ROM/ISBN 981-02-3594-1
To (un)subscribe, mailto:majordomo@ic.ac.uk the following message;
(un)subscribe xml-dev
To subscribe to the digests, mailto:majordomo@ic.ac.uk the following message;
subscribe xml-dev-digest
List coordinator, Henry Rzepa (mailto:rzepa@ic.ac.uk)