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> > In response, databases are evolving from SQL engines to data
> > integrators and mediators that offer transactional and nonprocedural
> > access to data in many different forms. This means database systems
> > are effectively becoming database operating systems, into which
> > various subsystems and applications can be readily plugged.
> Seems like an interesting starting point for thinking about the
> relationship between XQuery and SOA, and their relationship to other
Thoughts along the same line -- Jim Gray and Michael Rys of Microsoft, Andrew
Mendelson of Oracle, Rob High and Nelson Mattos of IBM.
1. Center of the Universe: The Microsoft View" (Jim Gray and Michael Rys)
Gray: "There are two parts to your question: the SQL/OO [object-oriented]
impedance mismatch and the SQL/XML data model mismatch. Let's take them in
Rys: "The first scenario is addressed by extending the SQL value space with an
XML datatype (both the ANSI standard SQL:2003 and Yukon provide this). This
allows SQL databases to operate on native XML data without the need for
shredding or marshalling. It bypasses the impedance mismatch by explicit
mappings of the more complex XML model to the relational model."
Rys: "There's not an impedance mismatch for query formulation if you take a
declarative query language such as XQuery. Many existing tricks can be applied.
For example, XQuery's FLWR iterator is well suited for parallelization."
2. "Center of the Universe: The Oracle View" (Andrew Mendelson)
Mendelson: "Oracle's approach to this impedance mismatch has been to converge
the SQL and XML technologies. Starting in 1997 with the release of Oracle 8.0,
we added object constructs to SQL in what was called object-relational
technology. ...This gave us the ability to rapidly add native support for XML
into the Oracle9i Database. XML Schema and XMLType are native to Oracle9i
Database, as are XSLT transformations and XPath traversal"
Mendelson: "Integrating messaging software and queues into the database provides
many development and operational benefits. Most business messages originate from
databases, and eventually update databases. Integrating the database and message
queuing software means the developers only need to learn a single product. They
only need to manage a single security and transaction model. The data types used
for the database are the same as those supported by the message queues, again
3. "Center of the Universe: The IBM View" (Rob High, Nelson Mattos)
Mattos: "While Web services give us a nice framework for connecting distributed
components, we need metadata to discover existing components or services, decide
how best to integrate them, and understand, once they're integrated, how they're
being used. [That understanding] allows us to tune the composed system. In other
words, the coupling of Web services and XML with the emerging metadata
frameworks gives us the hope of easier application creation and deployment and
more dynamic creation and tuning of services."
High: "There are some interesting corollaries between reliable messaging based
on persistent message queues and distributed databases. However, that's probably
not a critical rationale for tightly integrating messaging and databases. What
may be more compelling is the potential relationship of distributed notification
systems for signaling state transitions in loosely coupled, stateful services.
The messaging system can be used to register interest in state transitions."
======== Ken North ===========