Sun Microsystems and Microsoft have suspended years of bitter rivalry to release specifications for the delivery of single sign-on between systems that use the WS-* and Liberty Alliance standards for web services.

The interoperability was demonstrated on Friday at an event with Sun chief executive Scott McNealy and Microsoft chief executive Steve Ballmer.

Achieving interoperability between the two standards is the first tangible result of an agreement signed last year by the two companies.

The deal was part of a $1.95bn legal settlement over Microsoft's abuse of its monopoly on the desktop, and a licensing agreement for intellectual technology between the two companies.

McNealy and Ballmer admitted that the advancement is technologically minor. Microsoft last week unveiled an identity meta system that performs essentially the same task as the single sign-on technology demonstrated on Friday, but has a much broader scope.

However, the Sun/Microsoft collaboration demonstrates that a number of cultural differences between the erstwhile arch enemies have been resolved.

"It was like the time before the Berlin wall came down; there wasn't a lot of contact between folks from the East and folks from the West," said Ballmer. "We spent six months where our engineers were literally getting to know each other."

McNealy added that the engineers also needed time to determine the scope of the collaboration, and wanted assurance that the strategic direction had not changed.

"Once they [realised] that they just needed to make the technology play nice, and could still continue to innovate, everybody was comfortable," he said.

By working together the two companies have found a common enemy in IBM as they aim to erode the mainframe giant's market share. IBM unveiled its federated identity server last week.

"The world is moving slower than anyone predicted, but the backbone of enterprise computing is moving off the mainframe," said Ballmer. "We will disagree religiously about where they should go, but we will agree that they should go."

McNealy also leashed out at Linux in pitching Windows and Solaris as the only two viable operating systems.

"There are two clear survivors in the OS marketplace, and they both run on the x64 platform," he stated.

"They are volume players, they are supported by very large R&D budgets and they are Solaris and Windows. I'm not sure what is third place in the long term."

Jean Bozman, research vice president at analyst firm IDC, told vnunet.com that, although it has taken a relatively long time to reach single sign-on, the two companies will keep moving forward with the standard.

"This is a 10-year agreement [between Sun and Microsoft], but it has got to go deeper," he said. "They are on a good path and there is more to do."

Development teams from both companies, led by Microsoft chairman Bill Gates and Sun chief technology officer Greg Papadopoulos, will now shift their attention to delivering interoperability for Service Oriented Architectures.

Future interoperability enhancements also will involve storage, thin clients and systems management, according to the two executives.