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Date: 18 Oct 92 20:31:43 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!cs.utexas.edu!wupost!spool.m
u.edu!umn.edu!hecto.cs.umn.edu!hansen@ucbvax.Berkeley.EDU  (David M. Hansen)
Subject: Re: What is "real-time"?
Message-ID: <1992Oct18.203143.182@news2.cis.umn.edu>
List-Id: <comp.lang.ada>

In article <gsc.719318183@coombs>, gsc@coombs.anu.edu.au (Sean Case) writes:
|> hansen@micro.cs.umn.edu (David M. Hansen) writes:
|> 
|> >A better definition, I think (this is not original BTW), is that a
|> >real-time system must _manage_ time as a resource.
|> 
|> This is the definition I've been working towards for some time.
|> Do you have a reference for it?

Unfortunately, no, I don't.  To be honest, at the time I read this, I 
didn't much like it, although it did stick in my mind.  I believe I read it 
in Computer Language magazine about three years ago, and I believe it was
P. J. Plauger who wrote it, but I'm far from certain on either count.

|> 
|> >Certainly, it must meet all its deadlines (I imagine that word has
|> >an interesting etymology), but also it must delay taking action on
|> >a calculation if that calculation completes before its answer is
|> >required.
|> 
|> More generally, it must perform calculations taking into account the
|> time elapsed since its inputs were valid and the time that will elapse
|> before its outputs are used.
|> 
|> Consider a radar tracking system: it has a position for an object at
|> some point in the past, and must calculate where to look for it the
|> next time around.

Well put, I agree completely.

					-=Dave