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Home -> Community -> Usenet -> comp.databases.theory -> Re: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens]

Re: Does Codd's view of a relational database differ from that ofDate&Darwin?[M.Gittens]

From: Jon Heggland <heggland_at_idi.ntnu.no>
Date: Fri, 17 Jun 2005 11:08:29 +0200
Message-ID: <MPG.1d1cb1777ebcb8d398969b@news.ntnu.no>


In article <42b182de$1_at_news.fhg.de>, savinov_at_host.com says...
> What is strage here? It is precisely an example that I used.

Yes, the strangeness is the underspecification I described below.

> There is also another problem. Sometimes there are alternative (not
> unique) paths along which we can propagate constraints. In this case the
> database also cannot help but it is not its fault. The model simply does
> not define what path to choose (path is used in terms of COM).
>
> In UR it is a serious drawback bcause it is based on relational model
> (its spirit and fundamental assumptions), it is actually a complement to
> the RM. We need to look at the data differently in order to solve the
> problem.

I don't really consider this a problem, though. The different paths have different semantics, and the user should---no, must---be able to choose between them. Views and/or well-designed user interfaces can be used to make this more convenient. The (relational) database can indeed help. The ORM people have done nifty things in this regard, IIRC.

-- 
Jon
Received on Fri Jun 17 2005 - 04:08:29 CDT

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