December 20, 2000, 2:34 PM — The X Factor
STUCK IN TRAFFIC on the drive home? Log on to Food.com, a restaurant and delivery service site, from your wireless personal digital assistant and order Chinese takeout. What you see on that small screen is different from what you saw last weekend when you browsed the same site from your WebTV to order pizza during a commercial break. And tomorrow when you order lunch from your office, the display on the Food.com homepage will depend on the speed of the browser your company uses.
Why the customized displays? Because Food.com is using extensible markup language (XML) to specify the amount of text that is appropriate to display and how it should appear, depending on the browser and platform in use. That is possible because XML enables information to be tagged once yet formatted in many different ways. "When I first thought about XML, I focused on how it would streamline data delivery," says Rob Mayfield, chief architect at Food.com in San Francisco. "Now I'm looking at XML for rendering capabilities that allow me to customize the way our site displays content."
XML is an open standard for defining and sharing data on the web. Like HTML, it is a tag language, but it's more flexible than HTML and better suited for integrating data from a variety of sources. XML works well in applications that transfer data from one system to another, applications that offer different views of the same data and for electronic publishing.
Avalanche of Tools
Smart corporate developers like Mayfield are finding clever ways to exploit the extensibility of XML with the help of newly released application development tools. Within the last six months, a bewildering assortment of commercial and "open-source tools have become available. "It's a market that's all over the place. Every week there are new products that become available," says Douglas Barry, founder and principal of the database consulting firm Barry & Associates in Burnsville, Minn.
In general, XML tools are available in three price ranges. The most expensive are XML application servers with data storage capabilities. These typically sell for several thousand dollars per CPU. Some vendors that sell application servers also sell XML toolkits for several hundred dollars. For example, Bluestone Software's XML-Server typically sells for $3,000, but its Visual-XML developer toolkit is $99 a seat.
The second category includes downloadable versions of individual XML tools, which are often priced at around $100. Some examples of tool types are schema editors, translators and data extractors. For example, Extensibility sells XML Authority -- a tool for managing XML schemas, or graphical representations of the structures that appear in XML documents -- for $100 for a single-user license.