XML (Extensible Markup Language) is a markup language and file format for storing, transmitting, and reconstructing data. It became a foundational standard for data interchange on the web and in enterprise systems.
Origins
XML emerged from the W3C, with James Clark playing a key role in its design. It simplified SGML (Standard Generalized Markup Language) while retaining its extensibility, making it practical for web use.
Design Goals
XML prioritized:
- Human-readable: Text-based format anyone can inspect
- Extensible: Create custom tags for any domain
- Strict parsing: Well-defined rules for valid documents
- Platform-independent: Universal data interchange
Impact
XML became ubiquitous in:
- Web services: SOAP, REST payloads
- Configuration: Build tools, application settings
- Office documents: OOXML, ODF formats
- Data exchange: Industry-specific formats (HL7, XBRL)
Related Technologies
XML spawned an ecosystem:
- XSLT: Transform XML documents
- XPath: Query XML content
- XML Schema: Define document structure
- RSS/Atom: Syndication feeds
Legacy
While JSON has replaced XML in many contexts, XML remains essential for document markup, complex data structures, and industries requiring strict validation. Its influence on structured data exchange is lasting.