16.4 XML
HTML is fixed; that is, HTML has a predefined set of tags and each tag has its own semantics (meaning). HTML specifies how the information in a web page should be formatted, but it doesn’t really indicate what the information represents. For example, HTML may indicate that a piece of text should be formatted as a heading, but it doesn’t specify what that heading describes. In fact, nothing about HTML tags describes the true content of a document. The Extensible Markup Language (XML) allows the creator of a document to describe its contents by defining his or her own set of tags.
XML is a metalanguage. Metalanguage is the word language plus the prefix meta-, which means “beyond” or “more comprehensive.” A metalanguage goes beyond a ...
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