Re: relationship in the database

>>In Date's words 'a thin layer on top of the basic relational model'

>If you mean, can we translate an ER model to the relationa model,
>then yes, of course.

OK, but more importantly, do you agree that the RM model is more minimal than ER ?

And that it is sufficient - what is possible in ER is also possible in the RM?
If so, then for the sake of argument I will agree that the opposite (everything the RM can do, ER can do) could also hold in some extended ER model (that covers all the weakness that Date mentions regarding the ER model - if indeed it can even be called a model in it's current form).

I we agree with the above, then I come to my philosophical point that, to a large degree, I don't care if one model is more 'natural for people to think about' than another.

For one that is a very subjective test, and even if a 'is more natural' test could be commonly agreed upon, it _still_ does not imply that the answer is to use a 'more natural' model rather than to improve education and toolings so that the people can think in the terms of the more pure model.

I believe that the RM _is_ a phenomena. I would want very strong evidence that our brains are too thick to work with it directly before I would agree with packaging it up in a 'user friendly' but more complex form.

Or, before I sound too loony, I would want to see any 'packaging' of the model that makes it more palatable, to consist of user visible constructions standing on the foundation of the RM.

As an example, I am concerned about the INSERT/UPDATE/DELETE macros that most people seem to regard as the basic mutations operators in the RM. For example, in their SQL implementation, setting the value of a table to it's current value plus or minus a few rows, is statement of a completely different from from setting the value of a table to the value of another table plus or minus a few rows. I would hope that any SQL replacement does not make the same mistake.

Regards
Paul Vernon
Business Intelligence, IBM Global Services Received on Tue Sep 24 2002 - 11:15:43 CEST