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What is XML?

XML - (eXtensible Markup Language) is a text format for storing structured content. Unlike commonly used presentational document formats (used in word processors), XML format defines the structure of the content instead of its presentation.

The content of a sample XML document file may look like this: 

<?xml version="1.0"?>
<book>
   <title>What Is XML?</title>
   <para>
      <abbrev>XML</abbrev> - eXtensible Markup Language -
      is a text format for storing and sharing 
      structured content.
   </para>
</book>

In the example above, the book, title, para and abbrev are so-called elements in which text is contained.

What are elements in XML documents for? Elements describe the semantics of the content fragments in the XML document. For example, no matter what a title looks like in a published XML document, it is still the title by its semantics. And this refers to all the semantic units of a document.

XML Formats

The XML standard provides a markup syntax for a text file, i.e. it describes how text is wrapped into elements. The list of allowed elements for a particular document type is usually stored in a separate XML file called XML Schema.

For example, there are schemas for writing books (e.g. the Docbook format), office documents, technical documentation, description of medicines in the pharmaceutical industry, design documentation, and many others. And what's most important, anyone can create custom formats for their specific needs.

Publishing XML to Various Formats

Elements in XML documents serve in particular to facilitate the conversion of XML documents to different formats such as HTML - for placement on a website, PDF - for printing and distribution among people, RTF, and others.

How is it done? A separate file describes the style for rendering documents of a particular XML format. For example, the content of the <title> element in the example above can be rendered as bold with size 12, and so on, for every element with its specific rendering requirements.

Thus, on the one hand, the author doesn't think about document presentation but about its structure and content. On the other hand, if you need to change the rendering style, the changes will be made only to the stylesheet file but not to documents, which can be in large numbers.

The Benefits of XML


  • XML supports a lot of languages - Unicode.
  • XML is based on international standards and is widely supported by software manufacturers.
  • The hierarchical structure of XML is appropriate for describing almost any document type.
  • XML documents are simple text, free from licensing and any limits.
  • XML is independent of the operating system - XML documents work equally well on Windows, Linux, Mac OS X, and other platforms.

What is XML For You?

Having heard of XML at least twice, you are probably wondering what concern it is of yours. To get the answer, learn what XML means for your business and for technical writers.

Already aware of the undeniable benefits of XML but haven't the faintest idea what to start with? See our compact start-up guide to dealing with XML.

You can find more technical information about XML and related standards on W3C web site.