XML<\/a> is a versatile markup language that provides a standard way to structure, store, and transport data. Developed by the W3C<\/a> (World Wide Web Consortium), it is a simplified subset of SGML<\/a>. While HTML<\/a> is designed to display data, XML<\/a> is designed to describe data, making it a crucial component of the Semantic Web<\/a>.<\/p> An XML<\/a> document consists of Elements<\/a>, Attributes<\/a>, and Entities<\/a>. It must be well-formed, adhering to strict syntax rules such as case sensitivity and proper nesting. To validate the structure of an XML<\/a> file, developers utilize a Document Type Definition<\/a> (DTD) or XML Schema<\/a>. For data retrieval, XPath<\/a> is commonly employed, and for data transformation, XSLT<\/a> is the industry standard.<\/p> Modern applications leverage XML<\/a> for everything from Web Services<\/a> and SOAP<\/a> protocols to configuration files and Office Open XML<\/a> formats. Detailed specifications can be found at the official W3C site<\/a> and additional documentation is available through MDN Web Docs<\/a>.<\/p>