Re: Lucid statement of the MV vs RM position?

On 20 Apr 2006 14:41:30 -0700, "Pickie" <keith.johnson_at_datacom.co.nz> wrote:

[snip]

>There is a mindset about the Relational Model that is disturbing. The
>point of view that says that there is no TRULY Relational DBMS because
>of incompetance or wickedness on the part of the SQL DBMS providers is
>just outright wrong. The problem is that it is difficult in the

     IBM went with SQL over Codd's objections. Market inertia continued from there.

>extreme to build a data store of whatever size desired, that can have
>some arbitrarily huge number of people changing the data in it, and
>that will provide the answer to any conceivable query - as if the data
>store were to be frozen until the query is done. Every time you put an
>index in, or some other cute little wrinkle to more cleverly do this,
>you are argueably de-normalising your database. Well, you are storing
>data in multiple places, anyway.

     It does not matter what the implementation does as long as it is not visible to the programmer, that is, no dependencies on the physical are created.

>The idea of having a horrendously complex physical implementation - in
>order to provide the appearance of a clear logical model - is
>uncomfortable to me. I question, not the Relational Model, but whether
>implementing this aspect of it in this way is worth the trouble.

     Why? Have you ever used a compiler? Compilers create horribly complex lower-level code to implement a clearer (one hopes) higher-level language. Is this worth the trouble? Many would say so.

     What about having the same freedom from the lower-level details in a DBMS?

>Were there any formal definitions of the Heirachical and Network
>Models? I was going to write "exempting the ones that Codd set up in
>order to show the RM was better", but then I realised that I haven't
>even seen these, and that maybe they would teach me something. Does
>anyone have a link to them?

     Apparently yes, but they are much more complex. It is not that the RM is the only model possible, just that it is the simplest that works.

Sincerely,

Gene Wirchenko Received on Fri Apr 21 2006 - 01:08:03 CEST