Possible problems with Date & McGoveran View Updating

Alfredo Novoa wrote:
> Leandro Guimarães Faria Corsetti Dutra <lgcdutra_at_terra.com.br> wrote:
>>On Mon, 25 Aug 2003 11:57:09 -0700, Mikito Harakiri wrote:
>>> The examples of (still) open research topics include view
>>> updates
>>
>>Nice of you to ignore the nicest view updateability model
>>proposed by D&D...
>
> Do you mean by Date & McGoveran?
>
> I believe I have found some problems on it.
>
> Is anybody here interested in hearing about that?

Yes - what is your concern?

My primary concern is the rules for difference views; specifically, the part that says that the row to be inserted cannot satisfy the predicate for B in V = (A MINUS B). Suppose a row is presented for insertion into V that does not appear in either A or B at the moment, but could be valid in either. Does that mean that it is impossible to insert the row into the view? If the CJD and DMcG rules are as I understand them, I think the answer is "yes, it is impossible to insert into the view". I think I want the answer to be "no, you can insert the row because it satisfies the predicate for A (so it will show up in the view) and because it does not actually appear in B (so it won't cancel the appearance of the row in V)". This is a less stringent criterion than insisting that the row cannot appear in B.

-- 
Jonathan Leffler                   #include <disclaimer.h>
Email: jleffler_at_earthlink.net, jleffler_at_us.ibm.com
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