XML (Extensible Markup Language) is a markup language designed for storing and transporting data. It is designed to be simple, universal, and easily extensible, widely used in data exchange, configuration files, document storage, and other fields.
The main differences between XML and HTML include:
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Different Design Purposes
- XML is designed to store and transport data, focusing on data content and structure
- HTML is designed to display data, focusing on data presentation
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Different Tag Definition Methods
- XML uses custom tags, users can define their own tags as needed
- HTML uses predefined tags, the tag set is fixed
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Different Syntax Strictness
- XML syntax is strict, all tags must be properly closed, case-sensitive, attribute values must be enclosed in quotes
- HTML syntax is relatively loose, some tags can be left unclosed, case-insensitive, attribute values can be used without quotes
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Different Structure Requirements
- XML must have exactly one root element
- HTML can have multiple root elements (though not recommended)
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Different Whitespace Handling
- XML preserves all whitespace characters
- HTML merges multiple whitespace characters into a single space
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Different Nesting Rules
- XML requires tags to be properly nested
- HTML allows certain tag nesting errors
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Different Data Validation
- XML can use DTD or Schema for data validation
- HTML has no built-in data validation mechanism
Features of XML:
- Self-descriptive: tag names describe the meaning of data
- Extensible: users can define their own tags and attributes
- Platform-independent: can be transmitted between different platforms and systems
- Supports internationalization: uses Unicode encoding, supports multiple languages
In practical applications, XML is commonly used for:
- Data exchange in web services (such as SOAP)
- Configuration files (such as Spring, Maven configuration files)
- Data storage and transmission
- Document formats (such as Office Open XML)