I have worked in the RDBMS business for a long time. I want to understand the pros and cons of native XML DBS and RDBMS with XML capability before making a decision on our new Web transaction application. Sometimes, I have queries that RDBMS can be worked in Web environment through ASP or Java. Why do we need to use XML as part of the Web application?
If your data is such that it fits nicely into an RDBMS then it makes a lot of sense to leave it there. At the point where information is extracted from the RDMS for interchange or display, it makes sense to use XML for that.
Native XML database technology makes sense in some circumstances - complex hierarchical structures being the classic example.
Relational data is trivially represented it XML notation (for example a record set returned from an SQL query) but it does not have to be stored and maintained in native XML form. Indeed it often makes sense not to store it natively in XML in order to get all the retrieval and field indexing capabilities of the RDBMS.