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   Re: Query Languages for XML

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  • From: "Ingo Macherius" <Ingo.Macherius@TU-Clausthal.de>
  • To: jlapp@acm.org
  • Date: Fri, 14 Nov 1997 05:18:23 +0000

> Date:          Thu, 13 Nov 1997 22:47:51 -0500
> From:          Joe Lapp <jlapp@acm.org>
> Subject:       Query Languages for XML

Joe asks many questions I've asked myself, let me add some more.

> I am aware of the SgmlQL and SDQL languages, although I know
> only what can be gleaned from an hour's browsing on the web.

IMO there are three query languages, for each xml-part:
1) In XLL there are XLinks
2) In XSL there are the pattern parts of a rule
3) In DOM there a navigation functions that query parts of the grove

To me all those are similar in a high degree. So why was the DSSSL 
approach to have a single SDQL abadoned ? Why there isn't a 
"XML-query" draft, which is mapped to a concrete syntax by XLL, XSL 
and DOM ? There is much redundancy in this.

> BTW, Microsoft's XML-Data would be quite a boon for such a
> large XML repository.

Aren't XML-Data and MCF superseded by RDF (resource description 
framework) ? Are there features in XML-Data and MCF that are not to 
become part of RDF ?

> If the query language were in XML, it itself  would be extensible.

Agreed. This approach was taken by XSL. This is a strong feature, as 
one may use the same tools on document and meta level. There should 
be a query language in XML syntax, and it should be modularized. This 
query module should be imported by XSL, XLL and DOM.

The main obstacle is the fact thas XLinks and DOM API functions don't 
use XML syntax, for obvious reasons. But this feature is closely related to
namespaces (or architectural forms) questions, because ideally names 
need to be changed to fit the conventions of the importing language. 
This ain't easy, because DOM ist a programming language. In XML 
terseness matters, so do characters that have to be escaped in URL.
How can functionality and/or semantics of XML languages be mapped 
non-xml languages ? Do architectectural forms offer such 
functionality ?


Ingo Macherius // L'Aigler Platz 4 // D-38678 Clausthal-Zellerfeld
mailto:Ingo.Macherius@tu-clausthal.de    http://www.tu-clausthal.de/~inim/
Information!=Knowledge!=Wisdom!=Truth!=Beauty!=Love!=Music==BEST (Frank Zappa)

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