XML is everywhere. It used to interchange information. It is used to submit functions via SOAP and web services. It is used in the presentation tier and business logic tier. So, why change it. If your SOA application uses XML everywhere why change it into some relational format. Just store it in the DBMS as XML. That's what DB2 pureXML does.
Well that keeps it simple, but then the next question how do I get it into and out of the DBMS? We could do it the traditional approach of writing some application code in Java/C# to put the data into and out of the database via JDBC, but why not use XSL, SQL or stored procedures for this. Wait, but what does SQL and stored procedures have to do with this? Just like we suggested not to shread the XML into relational to store it, you don't have to transform it into some OO objects to process it.
Sounds hard! Actually with Data Studio data web services (DWS) it's easy. DWS allow you to take any DML SQL or stored procedure and drag and drop it into a web services. And that service could run as XML using Data Power. There is some very nice integration between DWS and data power and which you learn more about from Michael Schienker's blog entry.