Maybe you need an ORDB (Object-Relational DB) like postgresql. PGSQL supports Inheritance: http://www.postgresql.org Troy -----Original Message----- From: Luciano Ramalho [mailto:luciano@hiper.com.br] Sent: Monday, January 22, 2001 6:12 AM To: Tom Deprez Cc: Rik Hoekstra; zope@zope.org Subject: Re: [Zope] Object DB versus Relational DB ZODB with Data.fs is optimized to fetch data. Inserts or updates have a lot of overhead. It's the price we pay for the excellent versioning features. Therefore, when the are many we have been avoinding ZODB even when the problem domain calls for an OODB We have implemented a highly hierarchical database for a Yahoo-like directory using a recipe found in the book SQL for Smarties, by Joe Celko, ISBN 1-55860-323-9 (see Chapter 26 - Trees). Celko's solutions allow for a hierarchy with unlimited levels and, amazingly, it does not require sub-selects or any other construct unsupported by MySQL. The rest of the book is filled with solutions to problems that test the limits of the relational database model. Best regards, Luciano Ramalho Tom Deprez wrote:

...

A starting point is http://www.zope.org/Members/anthony/sql_vs_ZODB

Reading this text is exactly the problem I'm having. Unfortunately, it doesn't give much examples. I hope somebody can give me some answers on my question :

The problem I'm facing is the following. I've got a lot parent-child relationships -> OODB But, I also need to perform some queries on these records and link some to each other -> more RDB.

I'm not sure which way to follow. A hybrid solution isn't the best one, I think, because then you do twice the same work. ie. You've to create the parent-child relationship in the OODB (the site structure) and in the RDB (to perform correct queries).

The RDB solution is possible, but since I need lots of parent-child relationships not the best one.

The OODB is probably the best. However, this implies several

implementation

problems I don't know how to solve at the moment. Can somebody elaborate on the following questions? Thanks in advance.

Assume the following :

Group1 SubGroup1 SubGroupA Problem1 Examination1 Equipment1 Paremeters Equipment2 Parameters Examination2

....

Campus1 Room1 Equipment1 Equipment2 Room2

....

Now, if a person is creating a new equipment in Examination2. How can I show it all the avalailable equipments in Campus1? So this person can choose from it and create it in the examination2 folder? In an OODB environment?

If a person is browsing in Room1 and wants to get all the examinations which will be performed on Equipment1. How do I create such a query in OODB? (Or even further, the person wants to see all the examinations done on equipment1, but only with Group=Group1 and SubGroup=SubGroup1

How can this be done in Zope?

Thanks in advance,

Tom.

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