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The Core Features of XML

XML's design is guided by a few powerful principles that make it a cornerstone technology for storing, structuring, and exchanging data. While it may look simple, these core features allow it to be used in a vast array of applications, from web services to document storage.

Let's see the main features of XML and explain why it remains such an important tool in modern IT systems.

XML Separates Data from Presentation​

This is the most fundamental feature of XML. An XML document is designed to carry data, not to display it. It contains no information about how the data should be formatted, styled, or presented to a user.

Think of it like a recipe: the XML file is the list of ingredients and the steps (<ingredient>Flour</ingredient>, <step>Mix dry ingredients</step>). It contains the raw information. This single XML file can then be used in many different presentation scenarios:

  • An XSLT stylesheet could transform it into an HTML page for a cooking website.
  • A different program could format it into a PDF for a printable recipe card.
  • A mobile app could parse it and display it in its own native interface.

This complete separation between the data and its presentation makes XML incredibly flexible.

XML Simplifies Data Sharing and Transport​

In the real world, different computer systems often use incompatible, proprietary data formats. XML solves this problem by storing data in plain text.

  • Software and Hardware Independence: Because XML is just text, it is not tied to any specific application, operating system, or hardware. Any system that can parse text can process XML data.
  • Simplified Data Sharing: This makes it a "universal language" for exchanging information between different organizations or systems. A Java application can easily generate an XML file that can be read by a Python script or a C# service.
  • Simplified Platform Changes: When it's time to upgrade to a new operating system or application, your data is not locked into an old, obsolete format. As long as the new system can read text, your XML data remains accessible.

XML is Extensible and Self-Descriptive​

The "X" in XML stands for Extensible. Unlike HTML, which has a predefined set of tags (<p>, <h1>, etc.), XML allows you to create your own custom tags to fit your specific needs.

This feature makes XML self-descriptive. The tags themselves explain what the data represents.

<price>29.99</price>

Without any external documentation, a person or a program can immediately understand that 29.99 represents a price. This makes XML documents more readable and easier to maintain.

XML Increases Data Availability​

Because XML is a structured, text-based standard, it makes data available to a wide variety of "reading machines" beyond a standard web browser. This can include:

  • Screen readers for visually impaired users.
  • Handheld computers and mobile devices.
  • Automated news feeds.
  • Voice-powered assistants.

This accessibility is a direct result of its clean separation of data from presentation.

XML is a Foundation for New Languages​

Many other well-known internet languages are actually specific vocabularies of XML, created for a particular purpose. For example:

  • XHTML: A stricter, XML-based version of HTML.
  • SVG (Scalable Vector Graphics): A language for describing vector graphics.
  • WSDL (Web Services Description Language): Used for describing the capabilities of a web service.
  • RSS (Really Simple Syndication): The standard language for news feeds.
  • RDF (Resource Description Framework): A framework for describing web resources.

A Practical Example: A List of Emails​

This XML document represents a list of emails. It demonstrates all the key features in action:

<?xml version="1.0" encoding="UTF-8"?>  
<emails>  
	<email>  
		<to>Tom</to>  
		<from>Ryan</from>  
		<heading>Hello</heading>  
		<body>Hello brother, how are you!</body>  
	</email>  
	<email>  
		<to>Peter</to>  
		<from>Jack</from>  
		<heading>Birthday wish</heading>  
		<body>Happy birthday Tom!</body>  
	</email>  
</emails>
  • Extensible and Self-Descriptive: The tags (<emails>, <email>, <to>, etc.) were invented specifically for this purpose and clearly describe the data.
  • Data Separation: This file contains only the data. It says nothing about how the emails should be displayed (e.g., in a list, as individual panels, etc.).
  • Simplified Sharing: This text file can be easily sent between any two email systems, regardless of their internal architecture, and both would be able to parse and understand its contents.

Conclusion​

XML's core features (its extensibility, its separation of data from presentation, and its platform-independent nature) make it a powerful and enduring technology for structuring and sharing information.

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