XML Introduction

XML (EXtensible Markup Language) is a general purpose data description language. It looks very similar to HTML because it uses the open and close tag syntax as well as attributes. (Read the tutorial for info)

The main difference between XML and HTML is their use.

HTML is used to format a page for displaying. Most commonly used for displaying web pages in the Internet. HTML tags - For example, html, head, body, table - are predefined and used to create a "look" for a page in order to display it.

XML is used for storing and transferring data between different systems - For example, from a local database to remote database. These databases may not even be compatible or speak the same language. With XML, there is now a common language that they can use to exchange data.

The structure, or schema, of an XML document is completely arbitrary and is created by the author. XML documents can be structured so that data is easily written and extracted.

Here is an example of XML code:

    <BusinessCard>
      <Name>John Doe</Name>
      <Title>Sales Representative</Title>
      <Company>Some Company</Company>
      <Email>john.doe@somecompany</Email>
      <PhoneNumbers>
        <Office>(555) 555-1212</Office>
        <Fax>(555) 555-1221</Fax>
        <Mobile>(555) 555-2132</Mobile>
      </PhoneNumbers>
    </BusinessCard>


As you can see, XML is easily human-readable. There are also many widely available XML translation software packages that can translate XML to and from a variety of software systems including databases, EDI, and e-mail systems. You can also write your own translators in any programming language that reads and writes text.

You can more XML in this brief tutorial

For a more technical introduction to XML, please visit the W3C's page.