Re: Sensible and NonsenSQL Aspects of the NoSQL Hoopla
Date: Thu, 5 Sep 2013 02:04:08 +0200
Message-ID: <5227ca78$0$3170$e4fe514c_at_dreader36.news.xs4all.nl>
On 2013-09-04 21:00:22 +0000, Norbert_Paul said:
>> On 2013-09-04 05:28:01 +0000, Norbert_Paul said: >>>> Neither do I, and my compliments for the analyis. Am I right in reading >>>> some irritation between the lines that goes beyond a natural distaste >>>> for shoddy reasoning? >>> >>> Yes. The irriatation is based on bad personal experience within the >>> last three years. For example a (deliberate?) publication delay of >>> more than three years. There seems to be an extremely influential group >>> of researchers around the author where this kind of shoddy (thanks for >>> the new vocabulary) work is the only one accepted. Have a look at >>> "alternating hierarchical decomposition" (AHD). It just doesn't work >>> in 3D. >> >> Like this?: >> >> http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=5293499&tag=1 >> >> So the claim in the abstract about "scalable to any dimension" is wrong?
>
> Yes, exactly. Bulbul makes all proofs and examples in 2D. There, indeed,
> all seems to work. But Take a 3D cube, say [-1,1]^3, and its center point,
> say (0,0). Partiton that cube into the six pyramids with each cube face as
> its bottom and the center point as its apex (convec closure of a face and
> the center). Then remove three pyramids making sure that two of them
> are opposite. Apply the AHD and learn that it recurses endlessly.
> Reason: The convex closure of the shape is equal to the convex closure
> of its "differece shape" (aka difference to convex closure).
>
> An Ascii garphics illustration:
>
> *-------------------*
> / /|
> / / |
> / / |
> +-------------------+ |
> | . . | |
> | . . | |
> | * | |
> | / \ | +
> | / \ | /
> | / \ | /
> |/ \|/
> + +
>
>
> Example could not be published in 3D GeoInfo 2012.
> Reviewer: "good example, but explain why does it not terminate. What
> is the problem with their algorithm?"
> OK: The algorithm is so ill specified that you cannot establish a
> strict counter example for it. So I refrained from claimig that it will
> not work. Therefore I have just written
>
> ``However, with the shape
> $$\begin{picture}(75,90)
> \setlength{\unitlength}{1.5\unitlength}
> \put(0,10){\line(2,1){20}}
> \put(0,10){\line(5,4){25}}
> \put(0,10){\line(0,1){40}}
>
> \put(0,50){\line(5,-4){25}}
> \put(0,50){\line(3,-1){30}}
> \put(0,50){\line(2,1){20}}
>
> \put(20,20){\line(1,2){5}}
>
> \put(20,60){\line(3,-1){30}}
>
> \put(25,30){\line(1,-6){5}}
> \put(25,30){\line(1,2){5}}
>
> \put(30,0){\line(2,1){20}}
> \put(30,0){\line(0,1){40}}
>
> \put(30,40){\line(2,1){20}}
>
> \put(50,10){\line(0,1){40}}
> \end{picture}$$
> that method may not terminate.''
>
> to avoid backdoor arguments that sloppy specifications always leave open
> in the sense of "But I meant it that way ... ".
Impressive.
Is the description in the following not precise enough? (Only looked
briefly myself, busy day tomorrow, sorry.)
http://www.geocomputation.org/2009/PDF/Bulbul_et_al.pdf
Btw. it might be nice to see if there is no easy fix for this, like for
example cutting the difference shape in two. Intutively my first
inclination would be to base the proof of termination on the number of
vertices being reduced, which indeed in your conterexample does not
happen. This raises the question of how to do this optimally, for
certain definiitons of optimal (least number of nodes in the tree?).
>>> The problem is, when evidence is given, reviewers say that this is "too >>> abstract and technical" or they have an article wait forever to become >>> published. On the other hand, when a scientist's position is secured he >>> can make /any/ claim without any evidence. I thought this could be an >>> alternative channel here to post something critical. There is no >>> reviewing on comp.databases.theory. >> >> Indeed. But also not much of an audience. But who knows, it might come, >> and it's easier and less demanding (usually :-)) then a blog.
>
> Google archives Usenet. Maybe one day ...
Let's hope so. So let the record show you have also an arxiv paper on this: http://arxiv.org/abs/1205.5691
Btw. it has a few typos, you might want to quickly fix those now. ;-) Like "however, can expensive in dimension higher than 2"
- Jan Hidders