Re: Lucid statement of the MV vs RM position?

From: Marshall Spight <marshall.spight_at_gmail.com>
Date: 7 May 2006 17:54:35 -0700
Message-ID: <1147049674.976325.118020@j33g2000cwa.googlegroups.com>

Jon Heggland wrote:

>

> Perhaps I still was unclear; let me try again. Obviously you can
> postulate an aggregate operator that defined as iterated union, like SUM
> is iterated addition. Tutorial D does just that, and calls it (perhaps
> confusingly) UNION. You could call it GROUP instead, but Tutorial D does
> not. It uses the name GROUP for a unary relation operator that is
> shorthand for a particular extension/projection; alternatively a
> summarisation using that iterated union aggregate operator. I honestly
> don't see why this is so difficult to grasp.

You describe two things. You say they are different, but I don't see any differences.

One the one hand, we have "iterated union." On the other hand, we have "shorthand for a particular extension/projection", which is not very specific, but *could* be a description of what we have in the first case.

Can you be more specific about the differences between the two?

Marshall Received on Sun May 07 2006 - 19:54:35 CDT