ANN: XML and Databases article

[Ken North]

Subject: RE: ANN: XML and Databases article

>  Ronald Bourret wrote
> Steven R. Newcomb wrote:

> What do you mean by "different databases" here?  If you mean relational
> databases v. hierarchical databases v. object-oriented databases, then
> there's no problem -- I would expect each to have a different property
set.
> On the other hand, if you mean DB2 v. Oracle v. Informix v. SQL Server,
> then it seems there is something broken -- I would very much expect all
> relational databases to have the same property set.

There are a few points that haven't been made in this discussion.


It's a mistake to classify DB2, Oracle, Informix, and SQL Server as
relational DBMSs having the same logical data model.

DB2, Oracle, Informix, and Microsoft SQL Server are all SQL DBMSs, but the
first three are object-relational products. They have extensible
architectures so you can add user-defined types and  user-defined methods to
customize a database. You can add custom access methods and indexes by
writing server extensions. You can install Java classes in a database to add
types and methods
(http://www.devx.com/upload/free/features/javapro/1999/03mar99/kn0399/kn0399
.asp)

There is a distinction between an active database and a passive data store.
You can embed logic in active databases, so they can act as event alerters
and rule enforcers (e.g., reject data that isn't within a certain range of
values).

Finally, the days when SQL DBMSs stored only columns of number and
characters are gone. Some still do, but that is not a defining
characteristic. Most of the major SQL vendors moved to a universal server
model that supports rich types as well as traditional tabular data. For
storing an XML document, you have the option of decomposing it or storing it
as a whole.









query tool), not in others (wanting to expose tabular database




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