Patrick, I maintain the web page that Rupert mentions in responce to your message about Nextstep and Mach. (http://www.macos.utah.edu/Documentation/MacOSXClasses/macosxone/unix.html)
I'm curious to learn more about the development of Mach and its use in Nextstep. Can you point me to your sources -- preferably online so I can put them in the Bibliography section -- especially those that mention when Mach was turned into a Microkernel? -- http://mail.python.org/mailman/listinfo/python-list
