Data

• XML documents store data within tagged tree structures. Many Web applications use XML instead of a database, as other programming scripts can query the language, providing organized access to the data. The following sample markup code demonstrates a simple XML excerpt:
  
  <fridge>
  <item type="drink">Milk</item>
  <item type="food">Onion</item>
  <item type="food">Cheese</item>
  </fridge>
  
  The XML here models the data items as elements with attributes. The content of an element appears between its opening and closing tags, while the attributes appear within the opening tag. The XML elements are also nested inside the root "fridge" element. All XML elements can nest other elements inside them.
  
  

Platforms

• One primary advantage to using XML is that it is accessible across computing platforms. All the major programming and scripting languages benefit from standard libraries for processing XML data. This means that, as a developer, you do not need to handle the implementation details of creating or querying XML data within your applications, because you can make use of resources within the platform or programming language you are using to manage XML processing. XML is also a relatively "human readable" language, simple to understand even for people with little technical experience.
  
  

Standards

• XML allows developers to create and implement their own standards using XML Schema Definitions. Using an XSD, you can define the structures and syntax rules you want a particular set of XML data to adhere to. An XML Schema can define the elements, attributes and nesting rules for the XML within a particular project. This makes resulting applications more robust and reliable. When used within Web development, XML data can also help to create Web content that observes the W3C standards and recommendations, because it separates website content from presentation. XML is itself a W3C recommendation.
  
  

Flexibility

• Flexibility is key to the usefulness of XML. Developers can choose the markup structures that a particular set of XML data will contain. This can include element names, attributes, data types and nesting structures. This allows developers to tailor the structure of XML data to the needs of an application. Although XML data can include any user-defined element structures, it always remains accessible from other technologies, because the markup rules are standard, regardless of the elements or Schema in operation.