Re: What databases have taught me
From: mAsterdam <mAsterdam_at_vrijdag.org>
Date: Sun, 25 Jun 2006 02:54:38 +0200
Message-ID: <449dde52$0$31639$e4fe514c_at_news.xs4all.nl>
[snip]
>
> Neither of these provides an unambiguous specification of
> the problem.
>
>
>
> So, if all we are doing is converting bridges in to channels, how
> about INSERT INTO Channels (SELECT * FROM Bridges)
>
> But it would probably be better to provide an unambiguous
> definition of the problem. Perhaps a minimal example as well?
>
> Reading about the history of the analysis of the problem, coupled
> with the fact that I can't seem to find a decent explanation of it,
> woud seem to contradict this. Perhaps it is only not hard after
> one has already learned about it.
>
>
> Ah, you do have something up your sleeve. How about you just
> come clean with it and we talk about it?
>
> You know, the c.d.t. people are well aware of issue like transitive
> closure and Turing completeness, and how the traditional and
> various modern RAs stack up in comparison. We could discuss
> it if you wish.
Date: Sun, 25 Jun 2006 02:54:38 +0200
Message-ID: <449dde52$0$31639$e4fe514c_at_news.xs4all.nl>
Marshall wrote:
> Dmitry A. Kazakov wrote:
>> Marshall wrote: >>>Dmitry A. Kazakov wrote: >>> >>>>And, guys, what about presenting a query statement for building a dual >>>>graph?
[snip]
>>>http://mathworld.wolfram.com/DualGraph.html >>http://en.wikipedia.org/wiki/Planar_graph >>http://en.wikipedia.org/wiki/Dual_graph
>
> Neither of these provides an unambiguous specification of
> the problem.
>
>>It is a quite intuitive thing. I was born in St.Petersburg, but you can >>consider Venice for the same purpose. The graph of channels is the dual of >>one of the bridges. Regions are the islands + one for mainland.
>
>
> So, if all we are doing is converting bridges in to channels, how
> about INSERT INTO Channels (SELECT * FROM Bridges)
>
> But it would probably be better to provide an unambiguous
> definition of the problem. Perhaps a minimal example as well?
How about:
Given A planar graph G, compute it's dual graph G'
(this takes out the real hard part, BTW:
given a graph compute if it's planar)
If it is still unclear: just say what is the problem, I'll do my best. (It's in my 1974 graph syllabus, and very rusty :-)
>>>Is there some known theoretical complexity of this problem? (In other >>>words, are you just setting me up? :-) >> >>It is not hard.
>
> Reading about the history of the analysis of the problem, coupled
> with the fact that I can't seem to find a decent explanation of it,
> woud seem to contradict this. Perhaps it is only not hard after
> one has already learned about it.
>
>>The problem specifically for RA lies elsewhere.
>
> Ah, you do have something up your sleeve. How about you just
> come clean with it and we talk about it?
>
> You know, the c.d.t. people are well aware of issue like transitive
> closure and Turing completeness, and how the traditional and
> various modern RAs stack up in comparison. We could discuss
> it if you wish.
-- "The person who says it cannot be done should not interrupt the person doing it." Chinese Proverb.Received on Sun Jun 25 2006 - 02:54:38 CEST