Re: The Practical Benefits of the Relational Model

In article <j%yb9.18405$g9.57408_at_newsfeeds.bigpond.com>, mountain man <prfbrown_at_magna.com.au> wrote:
>
>2) I do not disagree. In fact it is my observation not from theory but
>from the production floor that has convinced me that "IN THEORY" there is
>nothing that cannot be expressed by the SQL at the RDBMS level.

Do you mean that SQL can express all queries? That's not true, it may often be in practice, but certainly not in theory; SQL is not computationally complete. Or do you mean that with SQL you can express all database constraints? That's also not true. Roughly speaking it only covers first-order logic.

>In practice however, one invariably finds that the bulk of this OI/BR/etc
>is in fact resident in the applications code and NOT in the RDBMS. This
>was my point.

Yes, but (1) you still haven't explained exactly what you mean with "OI/BR/etc" and (2) it's not clear whose fault that is. Many RDBMSs already allow you to formulate complex database constraints. What do you think is the problem then? Are the constraint languages not powerful enough? Is it not efficient enough? Are the application designer not able to formulate the database constraints in some formal logic? Or what?

• Jan Hidders