Dynamically extensible, Exokernel-based, provides many core services: scheduler, kernel threads, domains, event dispatcher, security mechanisms, primitive VM operations. Blurs distinction between kernels and applications, which traditionally live in user- http://www.cs.washington.edu/research/projects/spin/www/
Research OS coded in C++, architecture organized as frameworks of objects hierarchically classed by function, performance; customized by replacing subframeworks, objects; application interface is kernel objects exported via application/kernel protection l http://choices.cs.uiuc.edu/