Sun Microsystems and its allies will unveil the detailed workings of their Liberty Alliance specification Monday, providing competition to Microsoft's Passport service for easing the hassle of logging on to different Web sites.

Eric Dean, chief information officer of United Airlines and chairman of the Liberty Alliance Project, will release the technical specification at the Burton Group Catalyst Conference, the group said in an advisory.

Once the spec is out, Sun and others will be able to build "single-sign-on" Web sites and software that permits a computer user to log in once, then have that authentication serve other Web sites.

Sun, an Internet pioneer, has been to trying to reclaim initiative lost to IBM and Microsoft. Liberty is one part of Sun's effort to build next-generation Web services that are expected eventually to endow the Internet with new business and consumer utility.

Sun is counting on Liberty to become part of the pantheon of Web services standards and has been pushing to have such standards be royalty-free.

Microsoft triggered the Liberty Alliance formation through its Passport service, which serves the same function and which the Gartner Group says now has 14 million users. Passport was initially a Microsoft-only service, although the company has begun broadening it somewhat.

Sun countered with Liberty in September and quickly assembled prestigious backers, including Bank of America, Fidelity Investments, Sprint, Vodafone, Nokia, eBay, American Airlines and VeriSign. Later members included American Express, America Online, Hewlett-Packard and Visa International. Tech heavyweights IBM and Oracle have not joined.

Microsoft has said it would consider joining Liberty as long as it moved away from being a Microsoft-bashing club. Sun and Microsoft are bitter opponents.

Not that Microsoft is standing still. On Monday, the company unveiled a partnership that it says will allow the Passport system to authenticate Visa credit card users.

Sun would like to see Liberty grow from being a multi-company collaboration to a formal standard endorsed by the World Wide Web Consortium, said Jonathan Schwartz, who took over Sun's software business on July 1.

"I'd be thrilled to see it in the W3C," but that decision will be up to the Liberty Alliance partners and not just Sun, Schwartz said in an earlier interview.

Sun is also building Liberty support into its Sun Open Net Environment (Sun ONE) software. The first Liberty-enabled products--likely to be Sun's directory server software, widely used to store user name and password combinations--are expected in coming weeks, at least in beta form. That first product could be an "early access" version, not a fully supported one, Schwartz said.