Re: Ping: dawn, some mvl questions

mAsterdam wrote:
> Keith H Duggar wrote:
> > Precisely! There is a wealth of PHYSICAL information
> > lost whenever we change PHYSICAL representation.
>
> Your screaming doesn't make it more right.

The CAPS were for emphasis not screaming. And the emphasis was not part of the argument but rather part of the communication. I emphasized in hopes of avoiding key words being lost as I thought happened before when you made the statement

  "So let's lose the order? I don't think that is wise   always."

Since IMPLICIT was key (and you added universal qualification).

> The information itself is not physical. It is carried by
> physical media, allright.

Ok. No need for us to descend a spiral of semantics, so I will go along with you on this.

> 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).

I disagree. We do NOT preserve "whatever". Conversion from one physical system to another always loses something. Since this something is part of "whatever" we fail to preserve "whatever". However, I think we do agree on this point? Perhaps you have defined "layout" to satisfy your scanner implementation argument.

> We could choose to preserve some of what is in the layout
> by mimicking the original layout in your textfile.

Yes though "some" is key of course. And if we wish to preserve across physical implementations we had better make the "some" explicitly part of the logical model. That is part of Codd's point in 1970 1.2.1. Furthermore, if we wish to communicate the "some" then it must be made an explicit part of an agreed upon common model. (communicate, explicit, agreed, common).

> > 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.

You cannot deem information important without knowledge of it. Thus it is obviously always feasible to make known, deemed important information explicit. Your point applies to other information that is either unknown or deemed unimportant. Now sure, we may deem information unimportant that later turns out to be important. This happens all the time, particularly in scientific research. For example not measuring observables that later we theorize are important. Then the experiments must be repeated. However, this is a decision problem (or a fact of ignorance) not a problem with a logical data model.

> 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.

Sorry what precisely is the tautology? It's not really a semantics argument, it's an argument for a method. The method being: step 1) determine (deem) which information is important. step 2) make important information explicit.

Mistakes in step 1) have nothing to do with particular data models. As for step 2) I think we could employ a data model of our choice, relational being one of the options.

> > 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.

Ok, back where we started full circle. Seems we are not effectively communicating and I'm not up for stepping beyond common sense to a protracted semantics debate. It seems we do not share the same sense for words such as physical, logical, content, and perhaps implicit.

> > 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.

It's best to clearly state initially what you mean to say without relying on cliche analogies. Doing so will reduce the likelihood that translation is required. Especially when the analogy may be quite flawed as I believe this one is. Consider that the RMD has much more than just sets. Thus the "all you have is sets" is flawed right from the start.

More importantly, explicitly and clearly stating what you actually think may reveal important information. In this case you reveal that you categorize a relation as "one of several clumsy ways". Since, on the other hand, I find relations a quite elegant solution for ordering, we probably have little more to communicate on this particular topic.

• Keith --