Overview

This chapter introduces most of the basic standards for XML. If you are familiar with the syntax and the information model of XML, you can skip Section 2.2. If you are new to XML or need to refresh your memory, you will find this chapter helpful.

Schema definition is the subject of a long (and ongoing) debate in the XML community. We introduce its origins, derived from SGML (DTD), then discuss the now-released W3C recommendation XML Schema. We will pick up the schema thread again in Section 2.9, where we discuss techniques that go beyond XML Schema such as Schematron, architectural forms, and design patterns.

In between we discuss several standards that define access to documents, document composition, and document transformation, including XPath, XPointer, XInclude, XBase,XQuery, XSL, and the SAX and DOM APIs that allow access to document structures from programming languages. Please note that document transformation (including XSLT) is discussed in more detail in Chapter 9.

XML s history

The XML recommendation (Bray, Paoli, and Sperberg-McQueen 1998) was released in 1998 by the World Wide Web Consortium (the W3C). Initially the adoption of XML by the Internet community was quite slow because of a misconception. By many XML was seen as a successor to HTML. When it became clear that this was not the case (although XML deals with some of the deficiencies of HTML), but that XML is good for anything else but Web pages, things started to move. The adoption of XML by industry heavyweights such as IBM,...