Re: What does this NULL mean?

From: Alfredo Novoa <alfredo_novoa_at_hotmail.com>
Date: 16 Dec 2005 04:58:47 -0800
Message-ID: <1134737926.998663.46970_at_f14g2000cwb.googlegroups.com>


>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.

>> A relvar attribute is deleted in case of no integrity constraints
>> violation.

>Right. But who said that it should happen?

The catalog's designer.

> I, as a developer of this
>database, did not say that.

As a developer you are a catalog's user, and users don't dictate the rules.

> It happens because some anonimous developer
>of this concrete DBMS implemented it so. I cannot influence this
>bechaviou because it is hard coded. It is not part of my model. It is
>not part of my database. It is part of catalog hard-coded bahvior.

Just the same as your database for your users.

> This
>is only one example that catalog does not strictly obey to the normal
>laws of user-defined data.

I see a very strict obedience, only the roles change.

>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.

Regards
  Alfredo Received on Fri Dec 16 2005 - 13:58:47 CET

Original text of this message