Beyond web logs

eXtensible Markup Language (XML) has been widely adopted as a platform-independent format for data representation. It is useful for exchanging information among loosely coupled, disparate systems, such as in business-to-business (B2B) applications and workflow situations. Data interchange has been a major driver of XML technologies.

XML is increasingly present in enterprise applications that are used for modeling semi-structured and unstructured data. One such application is document management. Documents (e-mail messages, for example) are semi-structured by nature. If documents are stored inside a database server as XML, powerful applications can be developed such as:

• Applications that retrieve documents based on their content.
• Applications that query for partial content, such as finding the section whose title contains the word "Background."
• Applications that aggregate documents.

Such scenarios are becoming feasible with the increase in the development and availability of applications that generate and consume XML. For example, the Microsoft Office 2003 System allows users to generate Microsoft Word, Excel, Visio, and Infopath documents as XML markup.

Why Use Relational Databases for XML Data?

Storing XML data in a relational database provides benefits in the areas of data management and query processing. Microsoft SQL Server provides powerful query and data modification capabilities over relational data. In SQL Server 2005, these capabilities are extended to querying and modifying XML data. This allows your company to leverage investments made over past releases, such as investments in the areas of cost-based optimizations and data storage. For example, indexing techniques in relational databases are well-known. These have been extended to indexing XML data so that queries can be optimized using cost-based decisions.

XML data can interoperate with existing relational data and SQL applications. This means that XML can be introduced into the system as data modeling needs arise without disrupting existing applications. The database server also provides administrative functionality for managing XML data (for example, backup, recovery, and replication).

Native XML support within SQL Server 2005 is necessary to address increasing XML usage. Enterprise application development benefits from the XML support in SQL Server 2005.

The following sections give an overview of XML support in SQL Server 2000 and 2005, describe some of the motivating scenarios for XML usage, and include detailed discussions of the server-side and client-side XML feature sets.

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