Oracle Web Applications: PL/SQL Developer's Intro

Chapter 9. XML

Extensible Markup Language (XML) is an emerging standard closely related to Standardized General Markup Language (SGML), the granddaddy of all markup languages, which was designed by the U.S. government to create complex documents. Realizing that SGML was simply too complicated for his purposes, Tim Berners-Lee (the inventor of the Web) used SGML to create HTML, and the rest is history.

Now that the Web has matured, however, developers are starting to miss some of SGML’s capabilities. XML is an attempt to find a middle ground between the complexities of SGML and the ease of use of HTML. Like HTML, XML employs a tag-based syntax to mark up ASCII text. Unlike HTML, which controls the appearance of a document, XML describes the meaning and structure of a document by defining a syntax and grammar for creating new tags. XML is extensible because it lets you define your own tag vocabulary (as long as it follows the rules of the XML specification) for creating meaningful documents.

Although it’s currently being touted as “HTML done right,” XML is actually a lot more. It has a number of potential uses as a tool for integrating disparate systems and building electronic commerce systems. The XML specification provides an open framework for exchanging complex, structured documents (such as purchase orders, invoices, insurance claims, etc.) among different computer systems. In one fell swoop, XML eliminates network dependencies such as TCP/IP or IPX, protocol dependencies such ...