Short for 'eXtensible Markup Language.' A textual markup language for transferring structured data.

XML (Extensible Markup Language) is a standard for marking up structured data for messaging or storage. It is descended from earlier standards - SGML and HTML

An XML document can be defined by a schema defining its legal structure, and most languages support libraries or functions for manipulating XML documents. Many database management systems also support storage of XML data, either in an opaque blob or a native data type that allows searches and indexing. However, XML fields in relational databases tend to perform poorly.

Some database management systems use XML based structures natively. and others e.g. (some document databases) can store XML documents.

Another commonly used markup notation is JSON (JavaScript Object Notation). A comparison of the two formats can be found here.

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