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

From: Jon Heggland <>
Date: Fri, 17 Jun 2005 11:08:29 +0200
Message-ID: <>

In article <42b182de$>, 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.

Received on Fri Jun 17 2005 - 11:08:29 CEST

Original text of this message