Extensible Markup Language — a text-based format for storing and transporting structured data using nested tags that describe both the structure and content of the data.
XML uses opening and closing tags (like HTML) to organize data hierarchically. Each element can have attributes and can contain other elements or text. XML is human-readable and machine-readable, and is widely used for data exchange between systems, configuration files, and document formats.
XML is more verbose than JSON but supports more complex data structures and has a rich ecosystem of standards (XSD for schema validation, XSLT for transformation, XPath for querying). KML, GML, and many government data exchange formats are based on XML.
Example: A government agency exchanges property assessment data with a municipality using an XML format. Each property is represented as an XML element with child elements for address, assessed value, property class, and owner information. The receiving system parses the XML to extract and load the data into its database.