Re: What does this NULL mean?


"Alfredo Novoa" <alfredo_novoa@xxxxxxxxxxx> wrote in message
news:1134737926.998663.46970@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> >When we
> >are talking about catalogs and (conventional) databases then the
> >situation is the same. In principle, they can be viewed as one database.
> >However, they are at different levels so it is more appropriate to apply
> >different representation and manipulation methods for them (which do not
> >exist).
>
> A clear non sequitur. Like Paul said, there is an evident leverage if
> the schema can be managed like any other database.



> >Yes. And apply any concrete data model including RM to the problem of
> >global data management (catalogs, meta-info etc.) is also not very
> >appropriate.
>
> Why not?
>
> What is the alternative?
>
> The Hierarchical Model?
>
> Catalogs, meta-info, etc are data like any other. They don't have
> anything in special.

> >You simply create a new database using tools provided by
> >another database. For example, I could create a complex multi-level
> >system using Oracle. But the main problem is that Oracle database is
> >unaware what kind of system it manages. It thinks that it is relational
> >model while in reality it is something different. Instead, we need to
> >have a theory or a model that would allow us to create such multi-level
> >data models.

> You are missing the point. You don't have to create anything. The
> catalog design is a part of the DBMS implementation, and the developers
> don't have to design their own catalogs.
>
> What you could do is to design a better DBMS than Oracle.

> >Yes, of course we can apply RM to any data. But as I already mentioned
> >above, this model will be unaware that the data it represents has much
> >more complex meaning and hence it will not be able to help us in
> >managing this data. In this case we need to implement most of complex
> >issues ourselves. That is not the best way and hence the conclusion
> >could be that we need something new.

> I don't see any sense here. Any DBMS is completely unaware of the
> meaning of the data. DBMS only can check consistency and to perform
> symbolic manipulation.


I would agree with you but I have this one tiny problem:
How to enforce declaratively the integrity constraints on the catalog in
such a way that only a fully normalized schema can be developed.


.

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