XML stands for “Extensible Markup Language”. It is a versatile and standardized language for document markup. XML is known for its self-descriptive, human- and machine-readable text format.

Core Components

• Elements: The fundamental building blocks denoted by start and end tags, e.g., <name>John</name>.
• Attributes: Properties described within start tags, e.g., <book genre="fantasy">.
• Text Content: The data enclosed within start and end tags.

Key Terminology

• Well-Formed: A document that adheres to basic XML syntax rules.
• Valid: Goes beyond being well-formed to comply with a specific Document Type Definition (DTD) or XML Schema.
• Root Element: The topmost element in a hierarchical structure.
• Namespace: A mechanism for avoiding element name conflicts.

Relationship with HTML

While both are based on markup, HTML is a specific application focusing on web content, whereas XML offers a generalized framework. Unlike HTML, XML doesn’t come with predefined tags or a rendering mechanism; its strength lies in customizability and data structuring.

Common Use Cases

• Data Exchange: Widely employed in web services, APIs, and more for data transmission.
• Configuration Files: Many software applications use XML for their configuration needs.
• Document Management: Especially for data storage and retrieval in a consistent format.

Evolving Standards

XML has been instrumental in shaping various other technologies, including:

• XPath: For navigating and selecting XML nodes.
• XSLT: A tool for transforming XML content.
• XQuery: A query language tailored for XML data sources.
• XML Schema: A standard for defining document structure and data types.
• XML Namespaces: To avoid conflicts when combining XML vocabularies.