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From: willett@cbnewsl.cb.att.com (david.c.willett)
Subject: Re: The actual quote from the Post AAS article
Organization: AT&T Bell Laboratories
Date: Tue, 16 Mar 1993 14:54:22 GMT
Message-ID: <1993Mar16.145422.14034@cbnewsl.cb.att.com>
References: <1993Mar15.193135.29340@seas.gwu.edu>
Date: 1993-03-16T14:54:22+00:00
List-Id: <comp.lang.ada>

Mike Feldman wrote:

	{Initial Discussion about ATC Systems deleted}
>>
> Hmmm. My sources around FAA tell me that the main reason for Europe's having
> _fielded_ new ATC systems - In Ada - is that European air traffic is
> simply less dense than that of the US; there are fewer planes flying fewer
> corridors into fewer big airports. I know little about the internals of
> ATC systems, but general intuition and experience tell me that problems
> in this kind of system scale up perhaps linearly: 4 times the traffic 
> results in a system 4 times as complex. Maybe the "big O" is even worse.
> It would be nice if it were sublinear, but somehow I doubt it. 
>
	{Some Conclusions and Hopes for "lessons learned" deleted} 
> 
> Mike Feldman

It seems to me that the complexity of an ATC system would increase similarly
to the N-body problem from physics.  An example of such a problem is to
predict the motion of an electron travelling through a distribution of 
charges.  If memory serves, that problem is O(X**n) where N is the number
of charges and X is the number of electrons.
-- 
Dave Willett          AT&T Federal Systems Advanced Technologies
A Theoretical Physicist is one whose existence is postulated to make
the numbers balance, but is never observed in the laboratory.