Re: The Practical Benefits of the Relational Model

"Paul Vernon" <paul.vernon_at_ukk.ibmm.comm> skrev i en meddelelse news:aom513$ics$1_at_sp15at20.hursley.ibm.com...
> "David Cressey" <david_at_dcressey.com> wrote in message
> news:WOfr9.190$0I3.16276_at_petpeeve.ziplink.net...
> > In this context, who is a database "user"?
>
> Good question David as it is the key to my argument here. A user is
anybody
> (or anything) that has (been given) the right to access (at least some of)
> the data in the database, with whatever interface they desire (as long as
> ultimately the interface is just relational expressions).
>
> Now these users *cannot be trusted*. We must allow them to be stupid
and/or
> malicious and still maintain a working and integral database.

I believe the very fact that they are given access to (part of) the data implies that they are to be trusted to some degree.
>
> If users need to wait for other stupid/malicious uses to complete
in-flight
> transactions, then the database will not be useable. E.g.
>
> BEGIN TRANSACTION
> UPDATE table SET col = X
> <go on holiday for two weeks>
> IF RAND() > .5 COMMIT
> ELSE ROLLBACK
But this would be possible even with the D4- language - or? My impression is that if GoOnHolidayForTwoWeeks is a operator, the effect of table := table + < tuple>,GoOnHolidayForTwoWeeks() would have about the same effect.

> Traditionialy such problems are fixed by mandating database access only
via
> trusted 'applications', but going forward we should be looking at complete
> application independence for the RDBMS, which means that you cannot
*trust*
> the applications accessing your database.

Is that so? I must admit that i am not sufficiently familiar with traditional RDBMS applications, but my immediate guess would be that some time-out mechanism would be solved instead.
>
> Regards
> Paul Vernon
> Business Intelligence, IBM Global Services
>
>

Kind regards
Peter Koch Larsen Received on Fri Oct 18 2002 - 13:56:39 CEST