Re: Requirements for update languages?

"Jens Lechtenbörger" <lechtej_at_uni-muenster.de> wrote in message news:m2k7jo87eh.fsf_at_pcwi1068.uni-muenster.de...
> Dear reader,
>
> while there are some criteria to assess relational query languages
> (adequate, relationally complete, optimizable) I wonder what makes a
> good update language for a data model.
>
> In particular, I wonder about the following points in SQL.
>
> 1. I believe that SQL data manipulations are not adequate for bags,
> as they lack the ability to manipulate duplicates. (E.g., you
> can neither delete 3 out of 5 duplicates nor insert 3 duplicates
> at once.)

General comment on bags: There are no such things. If two things are *identical in all respects* then they *are the same thing*. If they are not identical in all respects and you choose to hide the piece(s) of information that distinguishes them, then you break the information principle and frankly deserve what you get.

> 2. As a db user, I expect that I can undo (inadvertent) data
> manipulations, e.g., undo an insertion via a deletion or vice
> versa.
> Does anybody else believe that this is a reasonable requirement?

No, I believe that is highly unreasonable. I you buy 5,000,000 shares you cannot just say, opps, didn't mean to do that - backout, you must sell them and hope you don't loose money.

> 3. As a db admin, I expect that users know what they are doing when
> they manipulate data.
> Does anybody else believe that this is a reasonable requirement?

No, I believe that is highly unreasonable. If all my database users had to pass am exam before using the db and had to sign a legally enforceable grantee that they know what they are doing, then I would not have very many db users. ;-)

> Basically, the anonymous referees did not buy (2) and (3).

I don't blame them.

Regards
Paul Vernon
Business Intelligence, IBM Global Services Received on Fri Nov 08 2002 - 21:09:54 CET