Sorry, I assumed I'd get replies from experienced real-time developers:
1) Determinism - the kernel has predictable and repeatable. It provides for some "deadline" (+/- any jitter). The worst case perfromance is known.
2) Hard Determinism - it MUST meet the deadline 100% of the time - or something blows up!
3) Soft Determinism - it "usually" meets the deadline. When using a "soft" deterministic kernel, what "usually" means needs to be quantified.