Chapter 6 Exchanging data with databases supporting XML

Why use XML in databases?

XML is becoming a universal data exchange format. An XML file can be read with any plain text editor. Most of relational databases (RDB) now support XML so that you can store or retrieve data through XML files.

With an XML model, you can generate an annotated schema that will allow you to store or retrieve data in a relational database supporting XML. To generate an annotated schema, you need to attach the appropriate extended model definition (XEM file) to an XML model mapped (or not) to a PDM.

The following table lists the databases supporting XML for which you can generate annotated schemas:

Database	Mapped XML model	Targeted XML language	Required XEM file
Microsoft SQL Server 2000	Yes	XSD or XDR	Microsoft SQL Server
Oracle 9i2	No	XSD	Oracle 9i2
IBM DB2 v8.1	Yes	DTD	IBM DB2 DAD

By attaching the SQL/XML extended model definition to an XML model mapped to a PDM, you can also generate SQL/XML queries to retrieve data in an XML format, from relational databases supporting SQL/XML.

The best way to generate SQL/XML queries is to use the XML Builder Wizard which helps you build an XML model from a PDM. The generated XML model is mapped to the PDM and automatically linked to the SQL/XML extended model definition. (See Generating SQL/XML queries)