Re: Data Constraints AND Application Constraints

"Paul" <paul_at_test.com> wrote in message news:423be58a$0$18400$ed2e19e4_at_ptn-nntp-reader04.plus.net...
> Kenneth Downs wrote:
> > I'd love to discuss the shape of that rules engine with you, and the
method
> > of implementation.
> >
> > For instance, it seems to me that Declarative Rules == Data Dictionary.
> > Meaning a body of declarative statements is essentially a series of
> > propositions about data. Or as we like to say, it is meta-data. So it
> > seems the real question is, what is the structure of the meta-data
tables?
> > The answer to that question determines the capabilities of your engine.
>
> Are we sure that check constraints are meta-data?
>
> They are just propositions, like the rows in tables are, only they are
> solitary rather then in a set of similar propositions.
>
> I don't think they are propositions about data, but propositions about
> reality.
>

I think the conversation between you (Paul) and Kenneth is really going in a productive direction. There are some real possibilities here.

But I think you are possibly about to slip into one of those definition potholes.

I'd like to suggest that "software" consists of data definitions, and prescribed actions on that data.
I'd like to suggest that constraints are really proscribed actions on data. As such, they can become part of the data definition.

The question of whether this part of the data definition is or is not meta-data is really a question of how the constraint is expressed. There are some database engines that have a really nice model of constraints, stored as meta-data in system tables. At least, they seem really nice to my untutored mind.

But the fact that constraints are part of a shared body of data definitions (data dictionary?) is really more fundamental than the question of whether or not they are meta-data.

Just my two cents. I have high hopes for this discussion. I hope I helped, rather than hurt. Received on Sat Mar 19 2005 - 12:59:42 CET