momentics wrote: > so, from the above, your point is that HRT system should have no > laxity on its deadlines?
I think the very nature of the definition is that a HRT system meets or exceeds timing constraints. If you say a HRT system is 150ns +/- 10%, you are really saying your absolute timing deadline is 165ns, to as many significant digits as you like. The mere fact you are asking/questioning with the term 'laxity' means it's not a HRT. A HRT has to be defined with some sort of absolute timing constraints, otherwise it breaks down to a SRT system with arbitrary constraints. > ie the granularity of measures lim(granularity)-> zero Well, this is a skewed representation. I like to think of it more like a logic based system. It either meets or exceeds timing constraints, or it does not. > like a mathematical abstraction (little's law) that it is impossible > to catch a tortoise up… Um, that story has lots of parameters that are not characterized as merely timing or deadlines, like the unpredictable/irrational behavior of the fox, Who cold have merely trotted into compliance (beaten the tortoise) and still have enjoyed frivolity along the journey. And yes that race did not have any specific timing constraint it was 'best effort' as we know there was not a specific allotted amount of time to finish, just who crossed the finish line first. That said, this story does mimic the arguments about hard/soft real time, as they are sheer folly..... It's all about latency, reliability(demonstrated via reproducible, timing constraint results), and on rare occasions, deterministic sub systems. A system that never fails is fault tolerant, until it actually fails. Just look at the telecom industry. Five nines of uptime (less than 5 minutes of down time per year on a phone switch is what the industry established, as practical matter of fault tolerance on a HA (high availability) system. It's not mathematically correct, but, it's good for business, and a practical trade off. Technical folks, particularly computer scientists, should fundamentally understand where science ends and where pop-science begins, in my opinion. James -- [email protected] mailing list
