Microsoft plans next year to launch middleware called HailStorm that would let its own applications and those built by independent software developers share data about a PC user's payment preferences, personal contacts, and calendar entries.

It's the sort of behind-the-scenes communication between software programs that Microsoft calls .Net, which aims to expand the company's purview beyond Windows PCs to generate new revenue. Rather than tying information about a user's address, contacts, application settings, and other preferences to applications using the traditional Windows method of associating objects in a client-server architecture, HailStorm software will rely on storing that data in XML documents and calling it across the Internet via Microsoft's Simple Object Access Protocol.

"The kind of dreams people have had about interoperability in this industry will finally be fulfilled by the XML revolution," Bill Gates, Microsoft's chairman and chief software architect, said at an event to unveil the initiative Monday. "It's really a necessary part of this revolution that we have services like HailStorm."

In demonstrations Monday, companies showed what these kinds of Web services could look like. American Express Co. showed an online bookstore application in which notifications of incoming orders would be displayed on a user's PC desktop running Microsoft's upcoming Windows XP operating system. XP would include Microsoft Passport, a digital wallet service available Monday that authenticates users with E-commerce sites and automatically fills in their payment information. AmEx's demo included the ability for a user to start an instant-messaging session with a customer-service rep, using HailStorm calls.

Groove Networks CEO Ray Ozzie demonstrated how users of Groove's peer-to-peer collaboration app could populate a list of people they wanted to invite to a session, from Microsoft's instant-messaging buddy list. HailStorm services could supply Groove with a central store of users and contacts, which the startup needs to propogate its app, Ozzie said.

The key to getting this type of integration to work across applications and platforms, of course, will be gathering a "critical mass" of software and customers, Gates said. "Stitching these islands together is about having a standard schema--in fact, a very rich schema--in which your information is stored." An early specification of the HailStorm schema, the set of XML fields that Microsoft and independent software developers need to agree upon to build apps like these, is available Monday. Microsoft plans more complete alpha software by this summer, a beta version of the HailStorm schema by the end of the year, and live services on the Internet sometime next year.

Microsoft's still working out pricing details, but plans to give away some services to consumers, charge for others, and implement fees for heavy users, or those wanting special technical support. There will be some revenue from licensing fees to developers and network service providers. And Microsoft may combine sales of HailStorm services with subscription versions of Office, which the company is developing.

Such scenarios could be years away, though. First up: getting data from Microsoft's MSN services such as Hotmail encoded into XML. Microsoft group VP Bob Muglia also promised not to mine, publish, sell, or target advertisements to data the company gathers while developing HailStorm.