The European Commission's warning against Microsoft this week -- like the US antitrust trial -- opens up questions not just about Microsoft's business behaviour, but about the complex ways in which Internet servers interact with client PCs. The EC Thursday told off the software giant for its practices in releasing information about client and server operating systems such as Windows 98 and Windows 2000, accusing Microsoft of using its dominance of the client operating system market to drive competitors in the server market out of business. Microsoft said it discloses all the necessary information in its Application Programming Interfaces (APIs), which it notes are freely available in bookshops and at conferences. Releasing more information than that, Microsoft said, would involve giving up trade secrets. Application Programming Interfaces (APIs) define how programmers can access another piece of code and use its existing capabilities. The question appears to be how much a server operating system vendor needs to know about the consumer version of Windows, which runs on 95 percent of all personal computers, in order to guarantee the server and Windows are completely interoperable. If Microsoft is holding back such vital information from some competitors, it could be in violation of European competition laws and face steep fines. But it is unclear what level of access OS designers need to Windows' secrets. Microsoft claims its API specifications are enough, but competitors are not so sure. In the absence of something like an open specification, such as exists with operating systems such as Linux, Microsoft can expect to rely on FUD (fear, uncertainty and doubt) to drive customers its way, competitors worry. Kirsten Ludvigsen, an analyst at IDC Research, agrees that the EU is right to ask whether Microsoft could be more liberal with information about its operating system. "If you leave out a third of the ingredients, the final meal won't taste as good," she says. "We think that Microsoft might be able to do a better job of writing API specifications." Competing server companies hope the EC action -- the beginning of a long legal process -- will clarify matters and, hopefully, lead to more open competition. "On the server side, there is no doubt about Microsoft's intention to bundle its different products and services together in a way that is difficult to separate," he says. "What we have seen continually is a business model that tries to leverage new technology based on a dominance in the marketplace," said Colin Tenwick, European vice president for Linux vendor Red Hat. Without some sort of action, Microsoft could end up taking over the server market as it has done in the client space, despite an inferior operating system, said Rudiger Berlich, UK managing director for Germany's SuSE Linux. "Certainly a ruling against Microsoft would weaken it and help companies gain more ground," he says. "It would help Microsoft users because there would be more competition and innovation. The EC launched its probe in February, coinciding with the launch of Windows 2000. What do you think? Tell the Mailroom. And read what others have said.