Appendix A. An Overview of XML

Throughout the book, there are many examples of how XML can be used within J2EE applications. Day 16, “Integrating XML with J2EE,” and Day 17, “Transforming XML Documents,” cover the topic of XML in some detail. This appendix is here to provide a quick reference that should enable you to comprehend XML examples used in this book.

XML is often described as portable data that co-exists alongside Java's portable code. Many new initiatives in Java use XML in a central role, so it is rapidly becoming a standard part of the Java developer's toolkit.

This appendix examines:

• The syntax and structure of an XML document

• Ways of defining XML structure, such as DTD and XML schema

• How different XML dialects can be identified