XML: Extensible Markup Language

What is XML?

XML (Extensible Markup Language) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. Defined by the W3C, XML is designed to be both human-readable and machine-readable.

XML is a versatile format used extensively in web services, configuration files, document formats (like Microsoft Office), and data exchange between disparate systems. Its self-descriptive nature and flexibility make it ideal for complex data structures.

History

XML was developed in 1996 by a working group organized by the World Wide Web Consortium (W3C). It was designed as a simplified subset of SGML, with the goal of being easily usable over the internet.

XML quickly became a cornerstone of web technologies, forming the basis for RSS, SOAP web services, SVG graphics, and countless other standards.

Key Features

• Self-Descriptive: Tags define the data structure
• Platform-Independent: Works on any system
• Extensible: Create custom tags and structures
• Hierarchical: Tree-based structure for complex data
• Unicode Support: Supports international characters
• Schema Validation: XSD and DTD for data validation
• Human-Readable: Easy to understand and edit
• Machine-Parseable: Widely supported parsers

Common Uses

• Web services and APIs (SOAP, REST)
• Configuration files for applications
• Document formats (DOCX, XLSX, ODT)
• Data exchange between systems
• RSS and Atom feeds
• SVG vector graphics
• Android app layouts and manifests
• Database import/export

Advantages

• Platform and language independent
• Self-descriptive and readable
• Extensive tool and library support
• Supports complex data structures
• Built-in validation mechanisms
• Unicode support for all languages
• Well-established standard

Limitations

• Verbose syntax leads to larger file sizes
• Slower parsing compared to binary formats
• Redundant tags increase storage needs
• More complex than JSON for simple data
• Requires more bandwidth for transmission
• Steeper learning curve for beginners

Technical Information

XML documents consist of elements defined by tags, attributes, and text content. Documents can be validated against schemas (XSD) or Document Type Definitions (DTD) to ensure structural correctness.