Introduction

The Extensible Markup Language (XML) was developed in 1996 by the World Wide Web Consortium's (W3C's) XML Working Group. XML is a widely supported open technology (i.e., nonproprietary technology) for describing data that has become the standard format for data exchanged between applications over the Internet.

The .NET Framework uses XML extensively. The Framework Class Library provides an extensive set of XML-related classes, and much of Visual Studio's internal implementation also employs XML. Sections 19.219.6 introduce XML and XML-related technologiesXML namespaces for providing unique XML element and attribute names, and Document Type Definitions (DTDs) and XML Schemas for validating XML documents. These sections are required to support the use of XML in Chapters 2022. Sections 19.719.10 present additional XML technologies and key .NET Framework classes for creating and manipulating XML documents programmaticallythis material is optional but recommended for readers who plan to employ XML in their own C# applications.