MSDN has posted guidelines for XML data modeling and usage in SQL Server 2005
Microsoft SQL Server 2005 provides extensive support for XML data processing. XML values can be stored natively in an XML data type column, which can be typed according to a collection of XML schemas, or left untyped. You can index the XML column. Furthermore, fine-grained data manipulation is supported using XQuery and XML DML, the latter being an extension for data modification.Read more
SQL Server 2000 and SQLXML Web Releases provide powerful XML data management capabilities. These features focus on mapping between relational and XML data. XML views of relational data can be defined using annotated XSD (AXSD) to provide an XML-centric approach that supports the bulkload of data, query, and update capabilities on XML data. Transact-SQL extensions provide a SQL-centric approach for mapping relational query results to XML (using FOR XML), and generating relational views from XML (using OpenXML). These supports have been extended in SQL Server 2005. Together with the newly added native XML support, SQL Server 2005 provides a powerful platform for developing rich applications for semi-structured and unstructured data management.
