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Re: Requirements for update languages?

From: Leandro Guimar„es Faria Corsetti Dutra <lgcdutra_at_terra.com.br>
Date: Mon, 11 Nov 2002 16:51:58 +0100
Message-ID: <aqojmu$buqn2$1@ID-148886.news.dfncis.de>


Jens LechtenbŲrger wrote:

> alfredo_at_nospam_ncs.es (Alfredo Novoa) writes:
>

>> On 08 Nov 2002 15:26:14 +0100, "Jens 
>> =?iso-8859-15?q?Lechtenb=F6rger?="  wrote:
>> 
>> With bags the view update problem is very diferent, and a lot more 
>> complex.

>
> Are you sure? Do you have a reference?

        We are sure.

        Sorry for not having a reference handy now, but think: the way to have a view (derived relation) updateable is to be able to derive the constraints that apply to the derived relation. This is a given in the relational model.

        Now think about bags. How could you derive the constraints in a "derived bag", and thus insert the data?

        Do you see a way? No? Neither does anyone else. To be more precise, a "bag model" has never being formally defined AFAIK.

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Received on Mon Nov 11 2002 - 09:51:58 CST

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