XML is a lot like Al Gore. You see it around a lot, you’re not quite sure what it does, and on the surface, it’s not all that darned interesting. What follows here is a sort of “state of the union address” on XML: What it is, what it’s doing, and the exciting promise it holds to redefine online communications and e-commerce.
Short for eXtensible Markup Language, XML was created so that richly structured documents — web pages, e-commerce transactions, vector graphics, mathematical equations, server APIs, and a zillion other kinds of information — could be read by both man and machine and used over the web. Think integration, think interpreter, think indifferent.
You may wonder, “Is XML similar to HTML?” Yes and no. Essentially, XML defines content, whereas HTML defines presentation. XML also uses tags to surround data, only you get to “invent” some of the tags yourself. You can’t do that with HTML.
The real power of XML, and its chief differentiator from HTML, is that a document that employs it can describe its own (data) format. One XML document may, in turn, be presented to its users with any number of technologies, including HTML.
Document Type Definitions (DTDs) are files used by XML to describe the format of a document by defining data tags, their order, and the nested structure of the tags. A validating parser (a kind of “spell check”) scrubs the DTD to verify that every required tag is awake and in its proper place in line. The payoff: An extremely powerful way to create industry standard methods of data exchange.
In fact, a number of industries are working on creating standard DTDs for interchangeable data. These vertical market standards will allow the industries to exchange data using either off-the-shelf software or homegrown solutions.
Consider an industry where interchange of data is vital, such as finance. Banks use proprietary systems to track transactions internally, but if they use a common XML format over the web, then they’d be able to describe transaction information to another institution or to applications like Quicken or Microsoft Money. Vendors like Bluestone Software, CommerceOne, Microsoft, and webMethods are supporting business-to-business electronic communications using XML.
Before XML, Dell duplicated HTML pages for each of its 17 country-specific web sites. Now, an XML application manages different languages, currencies, and tariffs for Dell Overseas. What’s more, Dell recently announced it will use an application based on XML as the interface between its customers ERP or procurement systems and its own online order management software. The real plus is that once used, Dell can reuse the same data structures for potentially all of its trading partners.
AT&T is planning to build an XML-based application that can access product and services information from disparate internal databases and publish that information in a personalized format on the web. No small task, given the fact that AT&T has had 100 years to build disparate legacy systems.
General Motors will provide its thousands of dealers and suppliers with web-based access to internal data, courtesy of XML.
NASA is using the highly extensible framework of XML APIs written in Java to allow astronomers to easily access telescopes and cameras in remote, inhospitable locations.
But not all is perfect on the XML front. Its huge potential for integrating applications and letting business partners swap data is beginning to become somewhat slowed by colliding consortia. According to an article in the May 31 issue of Internet Week, “Microsoft and IBM will almost certainly confront each other in their use of XML for enterprise application integration,” and “Others worry that too many cooks are stirring the XML broth.” Add to the mix the typical web browser incompatibilities, and you’re left wondering whether XML will ever truly supplant HTML as the standard web formatting specification.
Overall, you’ve got to like the possibilities for XML and its nearly unlimited potential in the binding together of legacy systems and industries on the web.