Re: Ping: dawn, some mvl questions

From: mAsterdam <mAsterdam_at_vrijdag.org>
Date: Mon, 22 May 2006 19:28:28 +0200
Message-ID: <4471f3f9$0$31642$e4fe514c@news.xs4all.nl>

Keith H Duggar wrote:
> mAsterdam wrote:
>

>>Keith H Duggar wrote:
>>
>>>If my grandmother hands me a recipe written on a piece
>>>of paper and I type it into emacs to store as a text
>>>file, do I lose information?
>>
>>Retorical, but I'll answer any, just to be specific:
>>Yes. Historians may come up with more, but here is some:
>>Her handwriting. Some of the layout.  The age of the
>>paper. Dents from writings on other papers.

>
> Precisely! There is a wealth of PHYSICAL information lost
> whenever we change PHYSICAL representation.

Your screaming doesn't make it more right. The information itself is not physical.
It is carried by physical media, allright. We could choose to preserve whatever is in the layout and the handwriting by scanning an image of the piece of paper (which is what many companies do, BTW). We could choose to preserve some of what is in the layout by mimicking the original layout in your textfile.

> Hence the great
> importance of developing a LOGICAL model and to make all
> information DEEMED important EXPLICIT rather than IMPLICIT.

As soon as we have perfect knowledge, we can do that. IOW it is a goal not allways feasible.
Some might be tempted to tautoligize the issue by stating that all implicit information is deemed unimportant by definition. However this also affects all derived data.

>>However, if she wrote it down in a particular order, not
>>based on the content, that order is exactly the
>>information you lose by sorting the ingredients by
>>quantity. You will never be able to reconstruct the source
>>order if you don't keep it e.g. by adding the original
>>line numbers in your plain text file.

>
> The key here is "not based on the content".

Indeed.

> That is the problem we must avoid.

Not if we have lists.

> For by content you must mean LOGICAL content.

Which, BTW, includes implicit content. Yes.

> Any information we wish to preserve across PHYSICAL
> representations MUST be made part of the logical content.

Now or later, yes. I thing the scanning example shows that some of the content can be made explicit later.

>>>If you want to use a logical data model that assumes
>>>some built-in implicit (physical?) order is meaningful
>>>nothing is stopping you. Though it is certainly not
>>>necessary to do so (the RM for example) and many have
>>>argued quite reasonably that such order dependence is a
>>>bad idea.
>>
>>So let's lose the order? I don't think that is wise
>>always.

>
>
> No I think you are missing the point or obscuring it.

Missing the point: maybe. I assure you I am not trying to obsure anything.

> The
> argument was against IMPLICIT or PHYSICAL order not order of
> any kind. To make sure other points are not lost key words
> in what I wrote here and before include: PHYSICAL, LOGICAL,
> IMPLICIT, EXPLICIT, DEEMED, AGREED, and COMMON.
>
>

>>I have only seen a priori dismissal of meaning of order,
>>coerced by the toolkit. Nails and hammers.

>
>
> Strange. I'm fairly new to most of these topics, however,
> even in my short study here I have seen well reasoned
> arguments against IMPLICIT and PHYSICAL order. For example
> see Codd 1970 1.2.1 for argument against depending on
> physical order and starting in 1.3 for arguments against
> dependence on implicit domain oder. Hence his proposal to
> deal with domain-unordered relations. I think dbdebunk has a
> paper (maybe several) on the topic. These were certainly NOT
> "a priori dismissal"s. Really, you can find a number of well
> reasoned arguments yourself if you try.

1.3 might be one, I'll check it.
I know it's out there somewhere (and I even have it on paper somewhere) but I couldn't find it at first google.

>>Maybe you can reiterate the reasonable arguments.

>
>
> I'm sorry no. First I don't feel qualified at the moment,
> second there is even a current topic in this group
> discussing list vs set, and third I'm sure you can easily
> find more references yourself in addition to Codd 1970.
>
> Finally, I really don't understand the repeated "nails and
> hammers" analogy in this context. Are you trying to say "if
> all one has is LOGIC everything is LOGICAL"? :-)

Do you really think that?

I'll translate: If all you have is sets, order is either lost or has to be made explicit in one of several clumsy ways. Received on Mon May 22 2006 - 12:28:28 CDT