Re: domain questionnaire

From: JRStern <JRStern_at_gte.net>
Date: Thu, 22 Feb 2001 16:11:46 GMT
Message-ID: <3a95381b.2337350_at_news.gte.net>


On 22 Feb 2001 09:18:19 GMT, hidders_at_REMOVE.THIS.win.tue.nl (Jan Hidders) wrote:
>Actually Codd has done that in the "second version" of the relational
>model: RM/T. Date discusses it in his latest book. See:
>
http://www.aw.com/product/0,2627,0201547325,00.html

Hmm, Amazon has just the main book at $72, wonder how a mere civilian orders the package offered here. Maybe the local university bookstore? Thanks for the pointer, I think I want the main book anyway.

>But for "higher level" data models such as ORM there are also good
>formal descriptions of their semantics plus a good philosophy
>(inherited from NIAM) about why and how it models reality.

Not sure I follow -- also in Date's book? Anyway, on the "why and how it models reality", I've read some of Date's stuff in random articles, and am not at all certain I agree with his assumptions, much less assertions.

>> Which is to say, that the issue of whether a database should reflect
>> an external ontology or not (and if so, how, and by what theory), I
>> think maps directly to this issue of how object identity must be
>> handled, ...
>
>I agree. I think it is reasonable to assume that if the database
>reflects an external ontology then every object should be somehow
>identifiable. (If you cannot identify the things you are talking about,
>then how do you know what you are talking about?)

Have you ever read the philosophical works of Ruth Garrett Millikan? I'm not sure she ever heard of computers or database, she's about philosophy of language and/or philosophy of mind, or thereabouts. I'm ploughing through this book, and in several years of looking for relevant theory, this is by far the best! She makes quite an issue of identifying versus classifying, ... I'm not certain I can summarize it here or apply it to database theory, not yet, but soon!

On Clear and Confused Ideas: An Essay about Substance Concepts Ruth Garrett Garrett Millikan

http://shop.barnesandnoble.com/booksearch/isbnInquiry.asp?isbn=052162553X

> What is not so
>obvious is that this should neccessarily be done by means of the
>attributes of the object. I think it is quite acceptable to have
>objects that are identified by a combination of some attributes and
>relationships.

I'm not sure even relationship is a necessary attribute. Identity does not have to be a relational thing at all, the relations can come later, between entities, that have an identity property orthogonal to the values of attributes and tuples.

>But if you are using the database to store objects as occurr in your OO
>program, then even that identifiability assumption may be too strong.
>Or is it? I am still not really sure about that.

Using the database as a persistent store has zero semantic load, it just has to work. The question is, where then *do* you put the semantic load? And, anyway, I don't even believe in "semantics" anymore, and this is a big change for me, who used to value semantics very highly "over syntax" in the area of computational linguistics.

Joshua Stern
JRStern_at_gte.net Received on Thu Feb 22 2001 - 17:11:46 CET

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