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

From: Jon Heggland <>
Date: Fri, 17 Jun 2005 12:34:53 +0200
Message-ID: <>

In article <42b29762$>, says...
> Technically the problem is that some joins are moved from queries to the
> database engine. Instead of transient joins with the scope of one query
> we make them persistent with the scope of the whole database. The
> queries are simpler and the joins can be executed more efficiently.

This is called views or virtual relvars in the RM. But what makes the joins more efficient? The equivalent of snapshots ("material views")?

> However, the main advantage is that our database now knows more about
> data and its relationships so now it manages these relationships (joins)
> rather that rows in tables.
> When we follow this way we obviously loose some freedom of manipulating
> data but the potential advantage is that data management is more
> reliable, more consistent and more efficient.

Ok, so it has some disadvantages. But how is it more reliable, consistent and efficient? Previously, you have mostly talked about how your model enables any query, no matter how vague or strange-looking, to be answered.

> Actually, the same high level goal is formulated for MS WinFS where they
> want all data items to be related

Why should all data items be related? They are not necessarily related in the real world; at least not in the subset of it we would want to model using computers.

Received on Fri Jun 17 2005 - 12:34:53 CEST

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