Re: Canonical DB

From: mAsterdam <>
Date: Sat, 24 Jun 2006 13:02:42 +0200
Message-ID: <449d1b74$0$31641$>

Dmitry A. Kazakov wrote:
> Gene Wirchenko wrote:

>> Dmitry A. Kazakov wrote:
>>> mAsterdam wrote:
>>>> These requirements establish K as a clean point type.
>>>> Aside: With the last condition deleted one can make a
>>>> circular K, having distance(k1, k2) <> distance(k2, k1).
>>> That won't be formally a distance, which is required to be symmetric.
>> Why must it be symmetric?  A to B and B to A may be different
>> distances if there are one-way routes involved.

> Rather when the space is anisotropic. If you just have many routes, you
> still could get a metric distance by choosing the shortest path.
> ---------------
> I found in Wikipedia that d(x,y) /= d(y,x) is called
> quasimetric space (I never met such thing anywhere else).

W = {Mon, Tue, Wed, Thu, Fri, Sat, Sun}

d(Mon, Fri) = 4
d(Fri, Mon) = 3

> Wikipedia also states that any
> quasimetric space can be made metric, by defining
> d*(x,y) = (d(x,y) + d(y,x)) / 2
> So it can be made metric.

Which is not always the sensible thing to do.

"The person who says it cannot be done
should not interrupt the person doing it."
Chinese Proverb.
Received on Sat Jun 24 2006 - 13:02:42 CEST

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