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   Re: [xml-dev] XML Data Modellling/Linking (was RE: [xml-dev] AfterXQuery

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On Fri, 22 Oct 2004 21:15:54 GMT, rpbourret@rpbourret.com
<rpbourret@rpbourret.com> wrote:
> Michael Kay wrote:
> >  What happened to the old doctrine of data independence?
> Hmmm... Sounds like the relational model. (Sorry, couldn't resist.)
> I think this could actually be dealt with at the query language level,

I hope you're not joking :-)  

The CODASYL data model ultimately foundered because of its unwieldy
links, and XLink foundered trying to do something similar for XML. 
Maybe the lesson here is that the relational model approach of
defining links *dynamically* based on relationships on the *values* of
information items rather than predefined links really is the way to do
what XLink tried to do.

The thing I always liked best about XQuery is simply the addition of a
Join operation into the XML corpus.  Until this thread I hadn't
thought of this as a replacement for XLink, but that idea is starting
to take root in my head ... it really might be worth a look back at
the struggle between advocates of CODASYL and those for the relational
model to see if there is a lesson there for us.  Date's little book
called "The Database Relational Model: A Retrospective Review and
Analysis : A Historical Account and Assessment of E. F. Codd's
Contribution to the Field of Database Technology" is the best summary
of this that I know of ...and the fact that Date and friends are
fervent opponents of XML should not  dissuade us from carefully
considering his analysis :-)

> Liam Quinn wrote:

> I actually think XQuery has so far failed to address its 
> requirement of supporting pointers/links,

Maybe that will turn out to be a Good Thing. The question in my mind
is not the thread-starter "what comes after XQuery" but whether  the
true power at the core of XQuery will remain visible and viable amidst
 the feature bloat and consequent delays of the spec itself.  
Potentially, this ability to do linking based on dynamic value
relationships could be XQuery's (or XQuery-minus-minus's ) greatest


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