Extensible Markup Language (XML) is a standard of the World Wide Web Consortium (W3C). XML focuses on the content of web sites more than on formatting. XML allows for the definition of additional specialized languages under XML syntax. Facilities of XML that allow for its extension into specialized vocabularies include namespaces and schemas. XML is meant to be both machine- and human-readable.
Because of its extensibility, XML focuses more on syntax and less on vocabulary. HTML composed under strict XML syntax is called XHMTL.
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