Re: Ping: dawn, some mvl questions

From: mAsterdam <mAsterdam_at_vrijdag.org>
Date: Tue, 23 May 2006 21:42:48 +0200
Message-ID: <447364d0$0$31651$e4fe514c@news.xs4all.nl>

Keith H Duggar wrote:
> mAsterdam wrote:
>

>>Keith H Duggar wrote:
>>
>>>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? :-)

>
> Yeah. From other statements you made it seems we agree on
> that. So this statement
>

>>>>We could choose to preserve whatever is in the layout
>>>>and the handwriting

>
> we agree is inaccurate. Replacing "whatever" by "some of
> what" would be more accurate.

Ok.

>>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?

>
> I think it would depend on my purpose.
> However, the solution
> I find "elegant" at the moment is the ID with an edge
> relation. I like it because it can represent any directed
> graph in addition to lists of course, you can have
> arbitrarily many DGs for a set of nodes, and since I still
> get stuck on "how" thinking sometimes, I can readily see how
> to efficiently implement such a relation and algorithms
> using it.

Let's see if I understand. We view the list as a very simple graph, the idea being that if we have a relation capable of describing any directed graph we surely can describe a list, right?

The drawback would be that the preservation of the listness is not garantueed.
Whithout additional constraints there
is no stopping anyone from inserting
nodes which make the described graph
more complex. Now the list is gone.

BTW it would be very similar to the "successive items" way (which also has this drawback), no?

>>>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.

>
> Well that is part of the /decision/ process. What I don't
> understand is why this /decision/ process is relevant to
> logical data models or their physical representation. For
> example, if we decide caution is best and that order may be
> important, then we temporarily deem it important and
> represent it in whatever data model we have chosen. Whether
> the model has lists or not seems irrelevant.

Let's go that way for now. Which relation representation of the list do we choose - is it consequential? If we have lists in our model, we may have performance penalties in our implementation, but no open door to misinformation.

>>>Thus it is obviously always feasible to make known,
>>>deemed important information explicit.
>>
>>That's optimistic, IMO.

>
> Why? If information is known and deemed important what is
> preventing us from making explicit? Can you give an example?

Not strictly an example, just a thought. In order to ascertain the importance of information it has to be observed (explicit information) or derived (implicit information) first. Think of an artefact from a crime scene - what information is there? The potential is huge.

>>Respect your ignorance. ;-)

>
> I have a HUGE respect for my ignorance ;-).

:-)

>>Say we have a list.
>>
>>We don't, at this time, know whether 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 whether 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.

>
>
> Adding an order attribute doesn't create any information it
> simply represents logically what was already there (physical
> order in the paper example). I can see that adding an ID for
> use in say a directed edge relation might add information in
> some sense to a paper list. However as far as electronic
> representations goes the ID attribute is simply making
> explicit what is usually implicit, references.

Well, I'm trying to get my finger behind that "some sense" by abstracting away from the paper and discuss lists instead - hopefully abstracting from the physical in that leap.

>>Hmm... I think there is more common ground than you
>>suspect at this time. No problem, I am patient.

>
>
> Yes I think so too. I think at the moment we differ mainly
> on what we consider "clumsy" and whether the "clumsy"
> relational solutions add information/misinformation.

Ok. I'm not even sure they do.
I'm just not convinced they do not.

[snip]

>>By keeping the list as a list no such awkward choice
>>has to be made.
>>
>>BTW, how is a list not logical?

>
> A list can be either physical or logical, implicit or
> explicit. These qualifications are key.

Lists as an abstraction (say "logical lists") are ordered by definition. The order is not explicit in the items, but in the way they are arranged. Is that explicit or implicit?
I don't know.
It's explicit if we know that the items are part of a list.

>>>>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.

>
> Ah I see. That is a manufactured tautology with some subtle
> context shifting (the phrase "can't be" which implies a
> future context, "information" and "explicit" may refer
> either to the source or the model representation, and
> "important" implies some alternate "objective" context) and
> as such doesn't reflect on anything we have discussed. This
> is more accurate (which I also quote in another form below):
>
> Some source information is deemed important.
> Information deemed important is modeled explicitly.

There is some resemblance to the CWA (Closed world assumtion).

> Thus
>
> deemed important -> modeled explicitly
>
> Which is not a tautology. Because of the context shifting
> your statement is ambiguous. Can you disambiguate by
> substituting appropriately?
>
> OD important -> SM explicit
> SM implicit -> OD important
>
> OD = { objectively , deemed }
> SM = { source , model }
>

Please keep in mind that this is about a hypothetical tautology that might be dreamt up by others - the ice to walk on gets rather thin here.

I shouldn't have done that. Sorry.

[snip] Received on Tue May 23 2006 - 14:42:48 CDT