Re: XML storing and management

From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Sun, 11 Nov 2007 12:44:35 -0400
Message-ID: <4737317f$0$5298$9a566e8b@news.aliant.net>

Jan Hidders wrote:

> On 27 sep, 22:52, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
> 

>>Jan Hidders wrote:
>>
>>>On 27 sep, 19:07, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
>>
>>>>Jan Hidders wrote:
>>
>>>>>On 27 sep, 16:27, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
>>
>>>>>>Jan Hidders wrote:
>>
>>>>>>>On 27 sep, 02:19, JOG <j..._at_cs.nott.ac.uk> wrote:
>>
>>>>>>>>Ok, so why is it exactly cdt, despite the inherent flaws of a
>>>>>>>>hierarchical model such as XML, it has seen such widespread uptake?
>>
>>>>>>>It's all hype, of course.
>>
>>>>>>>Btw., what fundamental flaws?
>>
>>>>>>Well, let's see... How about we start with: "The inability to re-order
>>>>>>the data without changing meaning and without destroying information." ?
>>
>>>>>"Hierarchical models such as XML" are not necessarily ordered-only
>>>>>data models. In fact most proposals for semistructured data models
>>>>>before XML weren't.
>>
>>>>>But even in XML this is not a big problem. Whether reordering destroys
>>>>>information or not depends on your interpretation of the data. If you
>>>>>send me an XML document and in addition tell me that certain parts
>>>>>represent sets then I can reorder them without destroying any
>>>>>information. The fact that XML is an ordered data model only implies
>>>>>that it *might* destroy informaton, not that it *must*.
>>
>>>>That's a nit. If one cannot always safely reorder, then one cannot
>>>>safely reorder.
>>
>>>I thought we were having a serious discussion, not playing trivial
>>>word games. My mistake.
>>
>>I am having a serious discussion. I am not the one picking at nits.
>
> I disagree. I think you are.

Suppose I said my pickup truck is no good for digging trenches. Your position amounts to saying: "If you hooked up a hydraulic system and welded a back-hoe on the back, it would dig trenches just fine."

One simply cannot re-order an arbitrary XML document without destroying information. One can re-order any relation without ever destroying information.

>>What your position boils down to is: XML is needlessly complex.

> 
> Not really. What I said is that concerning the aspect we were
> discussing it is actually missing a construct. So my position is more
> accurately described as that it is "too simple", not "too complex".

Actually, it is both, but I will accept the above correction.

>>As a
>>result of the needless complexity, one cannot re-order the data without
>>changing meaning and without destroying information.

> 
> That is too imprecise to be correct. You can in some sense always
> reorder if you want to. What I said is that whether this loses
> information or not is a matter of interpretation.

So, if I reorder all of the children of several nodes immediately after just one of those nodes, it's only a matter of interpretation whether that changed the meaning?!? You are joking, right?

  Note by the way that

> this is also true for the Relational Model: you cannot always
> arbitrarily permute the atomic values in a relation without risking
> changing its meaning. Also there it is a matter of interpretation
> whether this is actually a problem or not.

Could you provide an example?

>>BUT if we add even
>>more complexity, we can sometimes re-order data. Sometimes.
>
> Yes, when it is appropriate, which is not always.

So, it's too complex but adding complexity will sometimes but not always correct the problem. Sounds wonderful. Received on Sun Nov 11 2007 - 10:44:35 CST