Really. "This is the most important thing that will happen to the Web next year," says Bob Glushko, Tenenbaum's point man on XML and director of CommerceNet's for-profit spinoff, CNGroup. "XML," says Eckart Walther, product manager for browser leader Netscape, which, along with archrival Microsoft, has already climbed aboard the XML bandwagon, "is going to be as big as the Web itself."

Well, the Web itself is awfully big, but XML may render such breathless sentences prescient. Here's the pitch: Websites are built using markup languages--sets of rules for displaying information on a Web page. Today's standard language, HTML (hypertext markup language), was chosen at the dawn of the Web for its simplicity and the ease with which it combined pictures with plain text. This very simplicity, though, makes the Web in its current form a very tough place to do business.

Suppose, for example, you wanted to start a site called recipe.com that would let users scour the Web for that perfect low-cal poultry dish for 12. Any search engine can link you to 100,000 sites that contain the word recipe, and to 10,000 more that also mention low-calorie and chicken. But there's no easy way--short of looking at every one of those sites--to guide your customers to the recipe that's right for them. HTML simply lacks the software muscle to handle the business world's endless and complex transactions. "I call it Macbeth Multimedia," says Glushko, "full of sound and fury, signifying nothing."

In the past few years one eager start-up after another has rushed in to fill this vacuum, producing nearly 100 online commerce "standards," each vying to be the Web's one and only. Netscape and Microsoft, for their part, have responded by packing more and more proprietary software tricks into their increasingly unwieldy and overburdened browsers.

Into this software cacophony strides XML (short for extensible markup language). "It's essential that all these systems talk to each other," says Tenenbaum, "and they can't today, except at the level of HTML." The Web's original markup language made it easy for humans to read Websites; XML makes it easy for machines to read them. Think of XML as doing for the Web what Windows and the Mac did for personal computers. When you click on a document on a Windows-based PC, the operating system is smart enough to recognize that you've selected a word-processing document or a spreadsheet or a piece of E-mail, and to launch the appropriate application. XML makes Websites smart enough to tell other machines whether they're looking at a recipe, an airline ticket or a pair of easy-fit blue jeans with a 34-in. waist.

Created earlier this year by a team of programmers working for the World Wide Web Consortium and led by Sun Microsystems' Jon Bosak, XML lets Web developers put "tags" on their Web pages that describe bits of information in, say, a food recipe as "ingredients," "calories," "cooking time" and "number of portions." Using XML, your newly empowered browser no longer has to search the entire Web to find that low-calorie chicken recipe; it just has to locate the recipe sites and thumb through the relevant tags.

The same logic applies across the board. When XML kicks in sometime next year, after the Web Consortium finalizes its standard, any entrepreneurs who do business on the Net--travel agents, stockbrokers, pornographers--will need only to create a set of agreed-upon tags to make it immeasurably easier to buy and sell and communicate with one another and with their customers. This huge leap in efficiency will in turn help produce the explosion of online commerce the Web community has been impatiently waiting for. Pretty cool, eh?

Anyway, it was a sufficiently compelling pitch to shake loose some cash from the U.S. government. Last month a small consortium led by CommerceNet and CNGroup won a $5 million grant from the Commerce Department's Advanced Technology Program to promote the group's XML-based eCo (electronic commerce) system. The goal, says Tenenbaum, "is to bring together all the people in a given industry and say, 'Guys, let's sit down and agree on a set of core services.' That's how you build communities of commerce."

Sure, but as Clinton and Jiang will attest, sitting down is much easier than agreeing. Silicon Valley has already come to lawsuits over Java, the programming language for creating online applications that sit on top of markup languages such as HTML and XML. Now, although both Microsoft and Netscape have agreed to adopt XML (Microsoft's Internet Explorer 4.0 already supports some XML applications, and Explorer 5.0 and Netscape's Navigator 5.0, both due early next year, will support full-blown XML), each company seems to be maneuvering to make XML suit its own proprietary needs. Microsoft is using XML for its new Channel Definition Format for "push" media, and Netscape will integrate the new language into its upcoming Web-design software suite, code-named Gemini and due in mid-1998, hoping XML and Gemini will form the centerpiece of the network computer that Apple and Sun are building as an alternative to today's dominant Intel and Microsoft Windows PC standard.

XML represents terrain worth fighting over. It won't just make today's Web work better; it will also clear the way for countless new activities and enterprises that were too cumbersome to work on the Web at all. Say you're a frequent flyer who has purchased advance airline tickets in the middle of a fare war and wants to take advantage of any subsequent price drops. That's a service human travel agents can provide for you, but they're rarely motivated to do so. In tomorrow's XML world, it will be a simple matter for you to hire or create an "intelligent agent"--a kind of robot software program--that patiently monitors the industry's daily blizzard of XML price tags for favorable fluctuations, trading in your tickets for cheaper ones whenever the opportunity presents itself.

Tenenbaum--a longtime proselytizer for online commerce, whose Enterprise Integration Technologies developed much of the technology that makes Web transactions possible--believes that XML offers nothing less than "the real possibility of fundamentally restructuring the way a given industry works." If you can get everyone in, say, the real estate business--the brokers, the escrow agents, the mortgage banks--to adopt XML, says Tenenbaum, "you really can start to think about changing the rules: paperless closings, real-time mortgage bidding..."

Even in its infancy, XML tends to inspire daydreams at that level. Next year we'll find out how many of them actually come true.