Re: Requirements for update languages?
Date: Mon, 11 Nov 2002 16:51:58 +0100
Jens LechtenbŲrger wrote:
>> 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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