As you learned in the last chapter, the designers of XML had particular goals in mind as they developed the specification for the language. To help meet those goals, they designed XML with some rather strict structure and syntax rules. Although at first glance these rules might seem to make the language more cumbersome than, for example, HTML, you will see that XML includes a level of extensibility and aids in interoperability in a way that cannot be accomplished with HTML.
NOTE
An extensible computer language allows authors to extend or modify its syntax and semantics. Interoperability occurs when applications can share data.
In this chapter, we'll examine the logical and physical structures of an XML document and how the XML language is used to create these structures. We'll also look at the basic syntax of the XML language and compare it to HTML syntax. During the course of this chapter, we'll construct and discuss a simple XML document to demonstrate these principles.