Chapter 9: What Is a Native XML Database?

Overview

This book has examined XML from various perspectives. The first three chapters covered what are essentially programming basics. Chapter 4 examined basic SQL programming, used for retrieving datasets from relational databases. A basic understanding of SQL is helpful for understanding the basics of data retrieval for any database. Chapters 5 and 6 covered specific implementations of XML functionality contained within Oracle and SQL Server databases, respectively. Then I examined heterogeneous environments, which essentially use XML as a platform-independent method of passing data between different databases using XML to send messages. The previous chapter examined the object data model, which is very similar to XML document hierarchical structure.

Where Chapter 5 and Chapter 6 covered specifics of Oracle and SQL Server databases, this chapter attempts to conceptually refine some of the details covered in those chapters, and also to expand on much of what is covered in previous chapters. This chapter begins the process of describing native XML databases from a non-vendorspecific database perspective.

There are no Try It Out sections in this chapter as the content of this chapter is primarily concep tual, but also introductory with respect to native XML database standards.

In this chapter you learn about:

• What a native XML database is

• How an XML data type is a native XML database

• Schema-less native XML databases

• How many XML documents become collections of XML fragments in a native XML database

• Indexing in a native XML database

• The difference between document-centric and data-centric XML