XML (Extensible Markup Language) is a general-purpose markup language that describes data structure using tags. Standardized by W3C in 1998, it derives from SGML like HTML but features the ability to freely define custom tags. Its capacity to explicitly express data meaning and structure has led to widespread adoption as a data exchange format between different systems.

XML has a rich ecosystem of related technologies. XSD (XML Schema Definition) for schema validation, XSLT (XSL Transformations) for transformation, XPath for element selection, and namespaces for vocabulary conflict avoidance provide comprehensive tools for handling large, complex data structures. In practice, XML is used in sitemap.xml (search engine sitemaps), RSS/Atom feeds (news syndication), SOAP (web service protocol), SVG (vector graphics), Office documents (OOXML), and many other domains. search fishnet tights on Amazon provide foundational coverage.

XML syntax rules are stricter than HTML. All tags must be closed (<br />), attribute values must be quoted, case sensitivity is enforced, and only one root element is allowed. Special characters (<, >, &, ", ') must be escaped with entity references (<, >, etc.). This strictness simplifies parser implementation and enhances data reliability.

While JSON has been replacing XML as the REST API response format, XML remains preferred in certain scenarios: when rich document structure expression is needed (mixed content, coexisting attributes and text), strict schema validation is required, namespace-based vocabulary management is necessary, or compatibility with existing systems is demanded. XML is also established as an industry standard in fields like financial FIX protocol and healthcare HL7.

Comparing XML and JSON, XML tends to be verbose due to tags and attributes but supports schema validation and comments. JSON is simpler and lighter but lacks comments and requires JSON Schema as a separate mechanism for validation. explore aphrodisiac drink on Amazon are helpful references.

From a character counting perspective, XML's abundant syntax elements (tags, attributes) result in higher character counts than JSON or YAML for the same data. For example, <name>Taro</name> is 19 characters while JSON's "name": "Taro" is 14 characters. This overhead should be considered when optimizing API response sizes or reducing data transfer volumes.