XML DTD (schema) as database schema (DDL)

[Chen, Weijing]

No. In my idea, one does not store the original XML document as regular flat
file in a system. Instead stored as a parsed DOM tree or its like in a OO
database or relational database. The query engine will do the search work on
the tree based on XML-QL from user.

This advantage is that XML is more suitable to describe application domain
and data content than SQL. One don't have to twist the model and translate
into relational database. Alternative view could be that XML to OO database
is SQL to relational database.


Weijing Chen


> -----Original Message-----
> From: Dharmesh [mailto:Dharmesh at digitalmarket.com]
> Sent: Wednesday, October 20, 1999 6:39 PM
> To: Chen, Weijing; xml-dev at ic.ac.uk
> Subject: Re: XML DTD (schema) as database schema (DDL)
> 
> 
> Chen,
> 
> This is a good thought and will work for small applications.
> But the concern here is when you have a huge database. 
> Currently databases
> of the size of GigaBytes are pretty common and if you have a 
> XML file to
> represent it, I am sure it will be atleast 20% more in size. 
> Now if you run
> the XQL query on the file just imagine the preformance.
> Another thing to consider is the Join of the tables. The 2 
> scenarios are you
> have different file for each table or same file. In either 
> case creating a
> result set with a join will surely be a performance bottleneck.
> 
> Good application would be to have an object represented as 
> XML and passed
> across, so that the object can be instantiated along with the 
> behaviour from
> its XML representation. This is like serializing the object 
> but with its
> behaviour.
> 
> Regards,
> 
> Dharmesh Shah
> (dharmesh at xm.com)
> 
> ----- Original Message -----
> From: Chen, Weijing <wchen at tri.sbc.com>
> To: <xml-dev at ic.ac.uk>
> Sent: Wednesday, October 20, 1999 2:50 PM
> Subject: XML DTD (schema) as database schema (DDL)
> 
> 
> > Folks,
> >
> > I am thinking about using XML DTD (or its schema 
> specification) as a DDL
> to
> > define schema of a database. Following is the simularity of XML and
> > traditional SQL:
> >
> > DTD database schema
> > a huge XML document database table
> > XML query language SQL
> > small XML document SQL query result
> > HTTP ODBC, JDBC
> >
> > Now logically you are not storing data into traditional SQL 
> table, but as
> a
> > large XML document. Physically they could still relational 
> database, or
> > object database. The advantage of this is that XML is 
> object-oriented. It
> is
> > much easy and close to real application to model in XML than SQL.
> >
> > A step farther, one could use XML to model his specific 
> domain and provide
> a
> > query engine to handle the query and dispatch it to an 
> application module.
> > In this environment, there is not actually physical database but
> application
> > process running behind the scene. The user will have all the freedom
> > provided by XML query language to manipulate system as he 
> want. No more
> API.
> >
> > What your thought? Anybody out there build such framework?
> >
> >
> > Weijing Chen
> >
> >
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