After claiming last month that the open source model is flawed and "unhealthy", Microsoft senior vice president Craig Mundie is set to debate the issue at an open source conference in July. Mundie is expected to explain why Microsoft's vision of "shared source" software, where the software giant makes the source code of some of its products available to customers and partners while still maintaining the intellectual property rights, is better than open source. An open source application is one where users have the right to see and change its code, and are bound to freely distribute any changes they make. Michael Tiemann, chief technical officer of Red Hat, a company that sells a version of Linux -- the popular open source operating system and rival to Microsoft's Windows operating system -- will put the case for open source. The debate will take place at the O'Reilly Open Source Convention in San Diego on 26 July. Mundie attracted a storm of criticism after making his original comments at New York University's School of Business. In a speech, he argued that open source code can be a security risk and that those writing and releasing open source software such as the Linux operating system would not be able to create powerful, easy-to-use software broadly accessible to consumers. In a report issued around the time of his speech, Mundie also claimed that the companies who offer open source software to consumers don't have a valid business model. "A common trait of many of the companies that failed is that they gave away for free or at a loss the very thing they produced that was of greatest value -- in the hope that somehow they'd make money selling something else," wrote Mundie. Linus Torvalds, open source advocate and instigator of Linux, was unimpressed by Mundie's comments and accused him of disregarding the basic principles of intellectual property that have driven science for hundreds of years. "Mundie throws all that away, because he wants Microsoft to own it all, and to make tons of money from it," Torvalds said in an interview with Silicon Valley.com last month. The O'Reilly Open Source Convention will take place in San Diego, CA on July 26 at 8:45 AM. For details, see http://conferences.oreilly.com/oscon/ Find out how the open-source movement is revolutionising the high-tech world at ZDNet UK's Linux Lounge. Have your say instantly, and see what others have said. Click on the TalkBack button and go to the Linux lounge forum Let the editors know what you think in the Mailroom. And read other letters.