With the increasing use of XML for business documents and data transfers, interest is growing in Relational / XML Integration and the use of searchable repositories for XML-based data and documents.
The major database engines have provided their own distinct approaches for retrofitting storage of XML content, mapping to RDB table structures and exposing for structured query and update. In addition to the RDB add-ons, new purpose-built XML database engines have appeared. There is also growing use of XML as the method for packaging client/server queries and responses.
If you need Relational / XML Integration, or a pure XML database, SMH Systems are the XML and Relational Database experts who can provide the advice you need.