An Introduction to XML

XML stands for Extensible Markup Language. In simple terms, it provides a standard method for giving meaning to pieces of data, such that a computer will be able to understand and therefore properly manipulate and process that data.

Furthermore, if you were to share these data definitions with your customers and suppliers, their computers would be able to manipulate and process any data you subsequently sent them.

That’s all a bit vague … can you give an example?

Let’s assume you’re a book publisher, and that every week you send a list to your retailers of all new books. Suppose this week’s list contains the following:

The Iliad	Homer	$19.95
Hamlet	William Shakespeare	$14.95
The Lion, The Witch and the Wardrobe	C.S. Lewis	$24.95

It’s worth noting that a human reading the above can easily distinguish the book titles, author names and prices; a computer would have a much harder time. Using XML we enclose each piece of information between labels that describe each particular piece of data, giving us the following:

<book>
      <title>The Iliad</title>
      <author>Homer</author>
      <price>$19.95</price>
</book>
<book>
      <title>Hamlet</title>
      <author>William Shakespeare</author>
      <price>$14.95</price>
</book>
<book>
      <title>The Lion, The Witch and the Wardrobe</title>
      <author>C.S. Lewis</author>
      <price>$24.95</price>
</book>

The receiving computers could now methodically work through the above list, “knowing” the meaning of each piece of data. The receiving computers could, for instance, upload the data into the reseller’s database, then mark-up the books by 20%. They could do all this automatically because they can distinguish between the book titles, authors and prices.

Can I use XML to communicate with other companies?

Absolutely. In fact, organisations have been sending eachother electronic data for years. However XML offers several benefits over these other methods:

1. Open: XML is a standard of the World Wide Web Consortium, therefore it is freely available for all to use.
2. Widely accepted: Over the past couple of years the adoption of XML has boomed. Many of the most popular desktop products in use today have the facility to generate and read XML.
3. Extensible: XML was created as a highly flexible technology, able to grow and adapt to needs.
4. Multilingual support: the ability to support different languages is critical for any modern communications tool.

Perhaps most importantly, XML is freely available even for commercial use.

Sounds like it could be useful, but where could I use it?

The application of XML is really limited by the imagination. Here are some situations where XML has already been used:

1. Many news syndicates now offer news stories in a standard XML format. As a result, a computer programmed to accept this format can receive and manipulate news from most syndicates anywhere in the world.
2. In 2001, the European, US and Japanese Patent Offices along with the World Intellectual Property Organization began standardising their data around XML, facilitating the exchange of information.
3. The most popular desktop products for word processing and spreadsheets now allow the user to save their data in XML.
4. Realising the danger in offering exclusively proprietary solutions, virtually all of the best database products now allow for their data to be either accessed or exported in XML format.

However XML is not a technology used exclusively by large organisations: small to medium sized organisations can also benefit by storing and transferring much of their data in XML.

In closing

XML is a free, open technology which can assist with the exchange of information both within and across organisations. As the number of products and organisations that support this technology increases, it becomes ever-more important to consider using XML as a way of communicating information.