Re: What does this NULL mean?

>Catalog and (user defined) database belong to different layers. They
>have so big differences that cannot be viewed as one data model. Just
>for example:

I don't see any sense here. Two different databases cannot be viewed as one data model, that's plain absurd.

>For example, delete a row from a table in your database catalog. What
>happens then?

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

>Currently there are no appropriate tools for modeling catalogs and other
>types of meta information.

Currenty there are no appropriate tools for managing databases at all. But the catalog design is not an user's issue.

>That is not a simple issue. It is one of the most complex open problems.

Where are formulated these problems?

>For example, what if I need to create a catalog of catalogs?

You don't need that because the catalog should describe itself.

>> We can manage the schema applying all the power of the RM on the
>> catalog relvars.

>That would be the same as applying, say OOP, to the problem of
>manipulating data in general and schema in particular.

No, because OOP is not the best way to manage data and the RM is.

If the RM is the best way to manage any kind of data, and schema data is data then the conclusion is obvious.

Regards

   Alfredo Received on Thu Dec 15 2005 - 10:10:38 CST