INTRODUCTION

The Extensible Markup Language—XML—is a subset of the Standard Generalized Markup Language (SGML) specified in ISO standard 8879. SGML was created to create and maintain complex and portable documents to be used in highly scalable systems in a nonproprietary manner to any particular vendor. XML has become a key technology in the development of content for the World Wide Web. Today, with the birth of Web services, it is used for more than its original purpose of representing documents.

There are many excellent writings and books on the topic of XML. If you are not familiar with XML, you should probably stop here, familiarize yourself with the basics of XML, and then come back and continue. In this chapter, our intent is to outline some XML-based or XML-related technologies that are key in developing mobile applications.

To understand how and why XML is used in mobile applications, we should understand a brief history of how it came to be.

Brief History

In the beginning, there was SGML. And then, from SGML, came the less intelligent, but more likable son, XML.

If there were a bible of computer science, it would tell us the history of XML with a bit more flare. But, that essentially sums up where XML came from.

When the Web was first created, XML's sister, HTML, was born first.