An XML application is a markup language derived from XML rules, not to be confused with XML software applications, called XML processors in this book. An XML application is often a standard in its own right, with a publicly available DTD. One such application is DocBook, a markup language for technical documentation.
DocBook is a large markup language consisting of several hundred elements. It was developed by a consortium of companies and organizations to handle a wide variety of technical documentation tasks. DocBook is flexible enough to encode everything from one-page manuals to multiple-volume sets of books. Today, DocBook enjoys a large base of users, including open source developers and publishers. Details about the DocBook standard can be found in Appendix B.
Example 2.4 is an instance of a DocBook document, in this case a product instruction manual. (Actually, it uses a DTD called "Barebones DocBook," a similar but much smaller version of DocBook described in Chapter 5.) Throughout this example are numbered markers corresponding to comments appearing at the end.
<?xml version="1.0" encoding="utf-8"?>