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1.8.3. Great. So where do I start?


Up: 1.8. An Introduction to XML and the Text Encoding Initiative Previous: 1.8.2. What's the big deal about XML? Next: 1.8.4. Text Encoding Initiative

Extended markup language (XML) is a derived from the "mother of all markup languages,"108 Standard Generalized Markup Language (SGML). SGML was developed by the International Standards Organization (ISO) as a standard for designing data vocabularies.109 This means that you don't use SGML per se to create electronic documents, but that SGML defines a basic syntax and a set of "legal" elements from which you can then draw to create your own specialized markup language. In other words, SGML is a meta-language. A markup language created from subset of legal SGML elements to describe a particular type of document is called an SGML application, 110 or, alternatively, a document type definition (DTD). HTML, for example, is an SGML application (or DTD) developed especially for the description of Web pages.

SGML is very complex, however, and turned out not to be suitable as a universal language for delivering Web documents. In 1996 the XML Working Group of the World Wide Web Consortium (W3C) started developing a simplified version of SGML which could be used by communities to develop data vocabularies—XML DTDs—to describe particular types of documents.111 Michael J. Young explains that the XML syntax is more successful as a universal Web language because it offers fewer features and alternatives than SGML, so it is easier for people to read and write XML documents and for programmers to create applications to facilitate access and display of the information contained in those documents.112

Even though XML—via industry- and group-specific XML applications—is poised to become the lingua franca of the Web, this does not mean that HTML has been rendered obsolete. Indeed, HTML still remains the primary language for instructing browsers how documents should be displayed. While you can attach a cascading style sheet (CSS) to an XML document, which will allow you to view that document in a browser, a more common way of displaying XML documents is by using XSLT style sheets that convert XML documents into HTML for the purpose of display, while retaining the underlying semantic structure of the document itself.113

Up: 1.8. An Introduction to XML and the Text Encoding Initiative Previous: 1.8.2. What's the big deal about XML? Next: 1.8.4. Text Encoding Initiative



Date: last revised 2003-12-18 Author: Jennifer K. Nelson.
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