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From Stefano Mazzocchi <stef...@apache.org>
Subject Re: XML Database
Date Fri, 07 Jul 2000 19:05:26 GMT
Tim Bray wrote:
> 
> At 08:43 AM 07/07/00 +0200, Francois Wirth wrote:
> >Just want to know if anyone considered developing an XML driven database
> >like Tamino. I would be nice to work on an open source database that uses
> >Xerces, Xalan etc. for the XML processing. I know this is a huge project,
> >but I think there could be a lot of uses for this database and it would be a
> >challenging project. It could just be based on XML technology XQL, Soap, XML
> >Shemas etc.
> 
> Two comments.
> 
> 1. It's going to be really hard.  Core to XML are the notions of nested
>    structures, and of sequence being significant.  In particular XML's notion
>    of "mixed content" is devilishly hard to implement efficiently.
> 
> 2. The "market" (probably not the right word for free software) may not be
>    that big... XML is superoptimized for interchange, and a lot of people
>    who are using it are just using it pump data back and forth between one
>    boring old database and another.
> 
> 3. In a lot of cases, you can get perfectly good results by storing
>    small chunks of XML in a boring old relational database.
> 
> So to be honest, I'm not sure what the applications for a native XML
> database are.

If you are talking about stuff like

 <orders>
  <order id="384947988">
   <client>blah</client>
   ...
  </order>
  ...
 </orders>

then I'm totally with you. RDBMS will always kick ass on this no matter
what.

But if you have something like
 
 <article>
  <header>
   <abstract>
    <para><em>This</em> document is <keyword>XML
specific</keyword></para>
    ...
   </abstract>
  </header>
  <body>
   ...
  </body>
 </article>

no matter how you "chunk" your document into pieces, you are not able to
say "give me the abstract of every document that Stefano wrote", unless
the number of relational tables goes sky high and the SQL complexity get
incredibly big!

So, result:

 - small structure complexity XML -> Relational DBMS
 - big structure complexity XML -> XML DBMS
 
> Having said all that, people like Software AG are betting big bucks that
> there's a lot of people who want to do this (disclosure: I did a bunch
> of consulting for them back in '97-98) and they may be right.  And if
> someone around here wants to dive into this big ugly problem, that would
> be really cool.  After all, web servers aren't easy either, and back in
> '92 it wasn't obvious that very many people would need them. -Tim

I picture an XML DBMS more a piece of a XML content management system
rather than a "data" base. It's more of a "contentbase" than a
"database", if you forgive me the neologism.

The closest thing we have for a "contentbase" is CVS, but it's not even
powerful enough for being able to say "give me the abstracts of all the
articles that Stefano wrote, chronologically ordered, the first 10".

-- 
Stefano Mazzocchi      One must still have chaos in oneself to be
                          able to give birth to a dancing star.
<stefano@apache.org>                             Friedrich Nietzsche
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