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This first chapter introduces you to XML. It explains ingeneral what XML is and how it is used. It shows you howthe different pieces of the XML equaTIon fit together, and howan XML document is created and delivered to readers.What Is XML?XML stands for Extensible Markup Language (often written aseXtensibleMarkup Language to jusTIfy the acronym). XML is aset of rules for defining semanTIc tags that break a documentinto parts and idenTIfy the different parts of the document. Itis a meta-markup language that defines a syntax used to defineother domain-specific, semantic, structured markup languages.
XML Is a Meta-Markup LanguageThe first thing you need to understand about XML is that itisn’t just another markup language like the Hypertext MarkupLanguage (HTML) or troff. These languages define a fixed setof tags that describe a fixed number of elements. If the markuplanguage you use doesn’t contain the tag you need—you’reout of luck. You can wait for the next version of the markuplanguage hoping that it includes the tag you need; but thenyou’re really at the mercy of what the vendor chooses toinclude.
