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Re: 1GB Tables as Classes, or Tables as Types, and all that refuted

From: Alfredo Novoa <alfredo_at_ncs.es>
Date: Mon, 13 Dec 2004 12:49:49 GMT
Message-ID: <41bd8eba.9956390@news.wanadoo.es>


On Thu, 9 Dec 2004 20:42:18 -0600, "Dawn M. Wolthuis" <dwolt_at_tincat-group.comREMOVE> wrote:

>I can use an OO language to define a
>
>public class Relation
>
>just as easily as any other type, right?

Of course, but it does not mean that your class has anything to do with a relation.

>> It is not possible to use a class to define a relation type, but the
>> 1GB has nothing to do with defining a class such as "Person".
>
>So, you can use a class to define a relation, but not to define the type
>Relation, if I understand correctly.

You can have a class named Relation but you can not define a relation type with an OO language.

>That is what I thought, which is why I used the example of Person (which
>implements the interface "Relation" and could have a method of showAsTable
>in it). Where is the problem?

It has nothing to do with a relation type. The name does not make the thing. If not we could become very rich creating a class named OneBillionDolar :)

>Hmmm. So, the 1GB is only relevant when using OODBMS's

The 1GB consists into think that relvars and scalar types are the same, but the example of TTM is about OODBMSs and OR mappers.

>I'm probaby not using such a product, but I do have an imagination and
>cannot yet imagine what the blunder is. Even if this is only relevant to
>"persisting objects" in an OODBMS.

You can read the pseudocode I posted.

>> Of course there is, but only if you use an OODBMS or an OR Mapper.
>
>OK, so not just OODBMS's are the issue-- it is also an issue if you use an
>OO language and an RDBMS too, right? I just not seeing a problem, either in
>theory or in practice. cheers! --dawn

It is an issue if you are making a practical blunder because you think that relvars and types are the same thing, but in many cases it is hard to know what is the conceptual mistake that causes the practical blunder.

In the case described by D&D the confusion between types and relvars is evident, but in many OO apps I have seen the mistake seems to be that the programmers think that the SQL DBMS is only a weird transactional file manager and the information must be managed by the application using network (graph if you prefer :) structures, like in the old days.

Regards Received on Mon Dec 13 2004 - 06:49:49 CST

Original text of this message

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