Path: utzoo!attcan!uunet!seismo!dimacs.rutgers.edu!bcm!mailrus!wuarchive!emory!stiatl!srchtec!johnb
From: johnb@srchtec.UUCP (John Baldwin)
Newsgroups: comp.realtime
Subject: Re: Software primitives for real-time programming languages
Message-ID: <243@srchtec.UUCP>
Date: 27 Sep 90 23:12:10 GMT
References: <1853@tuvie> <232@srchtec.UUCP> <1889@tuvie>
Organization: search technology, inc.
Lines: 28

In article <1889@tuvie> alex@vmars.tuwien.ac.at (Alexander Vrchoticky) writes:
>
>Hmmm ... `graceful degradation' is a matter that is not necessarily
>directly related to the criticality of the system.

Agreed!

>The point is that there are systems in which missed deadlines are permissible
>and systems in which they are not; and there are systems which have a safe
>exit and systems which don't. These two concepts are largely orthogonal
>and should be treated as such.

Actually, I was thinking of a third possibility.  BTW, your examples
are *very* good at helping to bring all this to light...

The possibility I was thinking of is the case where *some* of your
task set have a safe exit state, and/or some of them can safely miss
their deadlines under certain circumstances.  It is nice to be able
to plan beforehand and say: under the following conditions, we know
that tasks A, B, and R will be preempted indefinately, while tasks
X and Y are still guaranteed to make their deadlines, which they MUST
in every circumstance.


-- 
John T. Baldwin                     | "Pereant qui ante nos nostra dixerunt!"
Search Technology, Inc.             | (A plague on those who said our good
johnb%srchtec.uucp@mathcs.emory.edu |  things before we did!)