Re: Object-Relational Databases

From: Gerhard Hübner <ghuebner_at_lrt.mw.tu-muenchen.de>
Date: Thu, 05 Aug 1999 15:39:46 GMT
Message-ID: <19990805.15394634@schoenfix.lrt.mw.tu-muenchen.de>

> I want to familiarize with object reletational databases, and I have
> some questions for introduction.

First, take a look at the greatest OO Technology repository:

http://www.cetus-links.org

> What is the difference with object relational databases and object
> orientented databases?

An object-oriented database has one or several language bindings. These bindings make it possible to directly and automatically map the =

classes in the project's programming language into the OO database. This mostly results in very few direct database API calls in the application code.

Object-relational databases don't have specific language bindings. You =

must manually care for the mapping with SQL statements.

> What is the difference between relational databases and object
> relational databases?

1.) ORDBMS should automatically create logical object ID (LOID) numbers which make it possible to create relationships that are value-independent. The LOID can be used as a primary key and does not =

change if the rest of the record is altered. Preferrably, the LOIDs are resolved using hash tables and not index lookups as hash table search occurs in constant time.

2.) ORDBMS should make it possible to model inheritance by means of sub-tables. Other object-relational mappings are too cumbersome, so check for subtables!

Best regards,

Dipl.-Phys. Gerhard Huebner        __
Institute of Astronautics          \ \____   "Heresy is another word
--------------------------------===>--____>   for freedom of thoug=
ht."
Technische Universitaet Muenchen   /_/       (Graham Greene)

Tel.: +49-89-289-16015, Fax: 16004
http://www.lrt.mw.tu-muenchen.de/personen/ghuebner Received on Thu Aug 05 1999 - 10:39:46 CDT