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From: hidders@hcoss.uia.ac.be (Jan.Hidders)
Newsgroups: comp.databases.theory,comp.databases.object
Subject: Re: The Theoretical Foundations of the Relational Model
Date: 25 Jun 2002 00:41:13 +0200
Organization: University of Antwerp
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In article <3d175923.10916296@news.verizon.net> you write:
>On 24 Jun 2002 18:35:46 +0200, hidders@hcoss.uia.ac.be (Jan.Hidders)
>wrote:
>>Er, a "physical order" in a logical/conceptual data model is an oxymoron.
>>
>>Easy for the user, sure, and defining such a data model is not difficult at
>>all. But can you give me a sound and complete axiomatization for this new
>>type of logic?
>
>It has zero effect on logical operations, it has positive benefit to
>whole applications, so why not allow it?

It is not true that it has zero effect on logical operations. If the
database has to maintain information about the order your updates become
more expensive. 

It is also not true that things always become easier for the user. He or she
now has to decide which tables are ordered and which are not. If the
ordering is important then you also need to introduce special update
operations such as insert-at(position) and move(position, position). You
will have to introduce special functions and predicates such as comes-before
and is-at(position) that operate on this order. Do you really believe that
this is going to make things simpeler for the user?

-- Jan Hidders