Re: RM VERY STRONG SUGGESTION 4: TRANSITION CONSTRAINTS

On 10 sep, 05:23, Brian <br..._at_selzer-software.com> wrote:
> I never mentioned anything about mutant tuples.  Tuples are values.
> Values do not change.

No, but you argue that the dbms should be aware of "which particular tuple in an update gets replaced by which particular tuple in the resulting database value".

It might be interesting to observe that exactly the same criticism was already expressed by Maurice Gittens a few years ago (he formulated it as "TTM does not allow tuple-level audit trails of updates". That is the very same thing you are complaining about). It has already been rebutted in a separate paper, and that rebuttal is now also a chapter in D&D's new book "Database Explorations".

The "mapping" you talk about does indeed exist.

It is that very mapping that the user applies when he decides which updates to apply to the database. That mapping involves real-world things. The DBMS cannot possibly observe those real-world things, and therefore, as far as the DBMS is concerned, it doesn't matter at all whether that mapping exists or not. The DBMS can't read that mapping anyway, so it must by definition rely on the user to apply that mapping correctly, and not be told lies by said user.

And you still maintain that you do not have a mental firewall smoewhere that is preventing this from entering your conscience ?

> What I'm proposing is a mechanism

Nowhere along the line in any of the two discussion threads have you ever "proposed" anything that was specified into sufficient detail to be worth being labeled a "mechanism". Received on Fri Sep 10 2010 - 09:45:05 CEST