Beginning XML, 5th Edition

Chapter 2

Well-Formed XML

WHAT YOU WILL LEARN IN THIS CHAPTER:

• The meaning of well-formed XML
• The constituent parts of an XML document
• How these parts are put together

So far you’ve looked at the history before XML, why it came about, and some of its advantages and disadvantages. You’ve also taken a whirlwind tour of some of the technologies associated with XML that are featured in this book.

In this chapter you’ll be examining the rules that apply to a document that decide whether or not it is XML. This knowledge is needed in two main situations: first, when you’re designing an XML format for your own data so that you can be sure that any standard XML parser can handle your document; second, when you are designing a system that will accept XML input from an external source so you’ll be sure that the data you receive is legitimate XML. There are, unfortunately, a number of systems that purport to export data as XML but break some of the rules, meaning that unless you can get the problem fixed at source, you have to resort to handling the input using non-XML tools. This makes for a lot of unnecessary development and defeats the object of having a universally recognized method of data representation.

Additionally, you’ll take a look at the basic and more advanced building blocks of XML starting with the most common, elements and attributes, and see how these are used to construct a complete document. You’ll also be introduced to the modern terminology that describes these constituent ...