Re: Ping: dawn, some mvl questions
Date: Tue, 23 May 2006 02:07:58 +0200
Message-ID: <447251a6$0$31640$e4fe514c_at_news.xs4all.nl>
Keith H Duggar wrote:
> 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.
Ok. To much usenet, I guess. I am used
to /this/, _this_ and *this*, (for resp. italics,
underlined and bold, some newsreaders even render
them so) but not to THIS.
Accepted.
> 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.
That would be /ascending/, in my view.
It don't mean a thing if it don't mean a thing.
If this is to poetic to your taste: data structures
have no reason to exist if the values they hold
do not (directly or indirectly) carry meaning.
Chris Date's use of an external predicate with every relation, necessary to interpret it's tuples into true propositions, serves this purpose.
>>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.
If this wasn't clear yet: I do agree with your observation on the loss from physical conversion (until all data is captured - after that lossless replication and duplication is possible). However, by retaining as much as we can of the whatever, we keep the possibillity open of capturing some more data from the same source (document in this case) later on.
> Since this something is part of "whatever" we fail to
> preserve "whatever". However, I think we do agree on this
> point?
Because of the physical conversions (and changes of context) it is impossible to retain all of the whatever. Is that what we agree upon? :-)
> 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.
Yep.
> 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.
Right. So, we have to postpone our decision on deeming things (un-)important we do not (maybe yet) fully understand.
> Thus it is obviously always feasible to make known,
> deemed important information explicit.
That's optimistic, IMO.
> 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.
Say we have a list.
We don't, at this time, know wether the order
in the list is significant or not (so excluding
situations where the order is alphabetic, size
or however evidently content-based).
We cannot, at this time, agree upon what the explicit order communicates (and wether or not it tries to communicate anything).
Now, when we only have relations to carry information (information principle) we have to either lose the order or add some attribute (an item number or a successor reference) to keep it - however, when we add this, we are creating either information or misinformation. At this point in time we have no way of knowing.
By keeping the list as a list no such awkward choice
has to be made.
BTW, how is a list not logical?
>>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?
Sorry, I thought that was obvious.
This is the tautology I had in mind:
All important information is explicit.
If it's not explicit it can't be important.
> 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.
Hmm... I think there is more common ground than you suspect at this time. No problem, I am patient.
>>>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.
'"all you have is sets" is flawed right from the start.' Agreed :-)
> 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".
No, there are several clumsy ways to represent
lists using only relations.
> Since, on the other hand, I find
> relations a quite elegant solution for ordering,
the "numbered items" way or the "successive items" way?
> we probably
> have little more to communicate on this particular topic.
Oh :-( Ok. Received on Tue May 23 2006 - 02:07:58 CEST