Communicating sequential processes

could be under isolation as well: no shared data concept to avoid multithreading problems.

It looks like the pendulum swings back to more process based parallelism instead of fine grained shared state parallelism through threads. The research-OS Singularity by Microsoft seems to separate plug-ins from the host application through processes. The plug-in and host can only communicate via interprocess communication. This decreases the chance for a plug-in to take over the host application considerably. And for simpler distributed systems design based on communicating sequential processes (here complete Java VMs) look at Jonas Boner, Distributed Computing Made Easy (link from theserverside.com)