Chapter 7. XML

IN THIS CHAPTER

• The Structure of XML

• Representation of Complex Structures

• Hierarchical XML

• The Document Object Model

• Commands to Move Data Between a Table and XML

• How FoxPro Implements XML

• Importing XML into Visual Basic .NET

• Reading XML into a Visual Basic .NET Dataset

• Using XML and Data Islands to Reduce Server Load

• Related Technologies: XPATH and XSLT

• Extensible Style Sheet Transformations (XSLT)

As we saw in the previous chapter, XML is instrumental in transmitting data between computers. Visual FoxPro 8 includes robust support for XML. In fact, Ken Levy, head of the FoxPro division at Microsoft, spent the majority of the past year building the XML editor for Whidbey.

In this chapter you'll learn a lot more about XML, and gain an understanding of its advantages in building database applications.

XML is the acronym for Extensible Markup Language . XML is Microsoft's replacement for the DBF. It stores tabular data in a text format that can be loaded and displayed as a table in any software. (And it doesn't have indexes, so it's slower than SQL. Hm, I'll bet Microsoft never thought about that. Maybe they'll add them so that you don't have to buy SQL if you don't want to.) But it's much more than that. It stores data in a way that makes it readable by other applications, in other locations, on other operating systems.

XML is the result of a collective effort of a consortium of firms and academic institutions to create a standard mechanism for the sharing of information, including tabular data. For our purposes as database developers, XML is mainly a method for describing the contents of a table in text form so that it can be reconstructed after being sent to a remote computer. In this sense, it does what a DBF does. However, several tables can be included in a single XML file, and hierarchies such as parent-child tables and their data can be represented in XML, neither of which can be done in a single DBF. And because XML works exactly the same way in any language and on any operating system, it's the ideal way to share data.