XML-Data: advantages over DTD syntax?

[Rob McDougall]

If I remember correctly, the advantages are listed in the spec.  The main 
advantage being that you can include the XML-Data definition within the XML 
file itself, so that you now can send a completely self-describing file 
that can be read by a single (XML) parser.

Rob
=======================================================
Rob McDougall            Phone:  (613)751-4800 ext.5232
JetForm Corporation      Fax:    (613)594-8886
http://www.jetform.com   mailto:rmcdouga at jetform.com
=======================================================

-----Original Message-----
From:	Paul Madsen [SMTP:paul_madsen at qmail.newbridge.com]
Sent:	Monday, September 29, 1997 9:46 AM
To:	XML DEV
Subject:	XML-Data: advantages over DTD syntax?

                                          9:31 AM             29/09/97

Hi, I posted this to comp.text.sgml but didn't get much response (thanks 
J.R.)
_________

The XML-Data specification from Microsoft
(http://www.sil.org/sgml/xml-data9706223.htm) proposes
that the logic traditionally expressed in the DTD (content models, 
attribute
lists, entity definitions,
etc.) be expressed using the syntax of XML instances instead.

For instance, instead of the DTD element declaration

<!ELEMENT book - - (p+) >

the XML-Data scheme rule would be something like

<elementType id="book">
     <elt href="#p" occurs="PLUS"/>
</elementType>

I'm attracted to the the idea if only because it seems "cool".

But what does this gain us? What deficiencies with the DTD formalism does 
it
address?

Is it the ability to extend object types so that one class of object is a
specialization of another more
general class?

Do not Architectural forms provide the traditional DTD syntax just that
ability?

Thanks for any insight.

Paul


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