Re: database market share 2003

"Noons" <wizofoz2k_at_yahoo.com.au.nospam> wrote in message news:40d172f7$0$6203$afc38c87_at_news.optusnet.com.au... [snip]
> Yes, but even IMS has a data storage theory behind it. Hierarchical
> databases.

That's arguable. In some ways Codd's greatest achievement was simply showing that theory could be usefully applied to databases. Most pre-relational databases did not have much theory behind them, certainly nothing that could be regarded as a complete model. A better characterisation would be that the implementations and/or specifications came first, and only later did the more theoretically minded try to elicit abstract models from the mess of detail.

Taking the example of the network model (and I believe the point holds for the hierarchal model also) and quoting from Date again.

http://www.intelligententerprise.com/db_area/archives/1999/991105/online2.jhtml

<quote>
a.. First of all, Codd realized that to compare the very concrete CODASYL specifications and the much more abstract relational model would be an apples-and-oranges comparison and would involve numerous distracting irrelevancies.

a.. Hence, it would be necessary first to define an abstract "network model." The comparison could then be done on a level playing field, as it were, in a fair and sensible manner.

a.. Codd therefore proceeded to define an abstraction of the CODASYL specifications that might reasonably be regarded as such a model.

Thus, Codd has some claim to being the first person to attempt to give an abstract definition, not just of the relational model (of course), but also of a network model! Certainly none of the CODASYL documents ever attempted any such thing
</quote>

BTW if you want to continue this arm of the thread, I suggest you start a new thread in comp.databases.theory.

Regards
Paul Vernon
Business Intelligence, IBM Global Services Received on Thu Jun 17 2004 - 07:56:02 CDT