Thread: Theory!!

Mayra wrote:
> hi,
>
> can anyone give me some info on the caracteristics of object
> relational databases and their advantages as well as disdvantages!

I'm not sure that there is any standard definition of "object relational
databases". You also don't say what you want to compare them to. Could
you provide more detail - what precisely are you trying to find out?

--
   Richard Huxton
   Archonet Ltd

> can anyone give me some info on the caracteristics of object
> relational databases and their advantages as well as disdvantages!

First, it's best to understand the real concepts behind relational
databases. I read two great books that taught me a lot about the theory
of RDBMSs, and why they were developed (and why RDBMSs have been so
successful).

(1) "An Introduction to Database Systems", by C.J. Date -- A great book
about the theory that's very precisely written. The book leaves no
ambiguity in it's explanations, and covers a lot of ground.

(2) "Foundation for Future Database Systems", The Third Manifesto, by
Date and Darwen -- An explanation of what features should be part of a
complete RDBMS, and which should be left out, and why. Again, this
author is very good. If you've read the first book, and you're still
lured by the buzzwords in the database world, this second book will cure
you :)

Object oriented development is the way you structure your application,
and more important, the way you understand your application. You don't
need object oriented syntax to develop an object ordiented application.

PostgreSQL does, however, provide some object oriented syntax: for
example, inheritence. In some cases, using inheritence (versus a similar
solution without) can affect the way data is stored physically, which is
helpful to some (even in non-object-oriented contexts). However, the
inheritance doesn't add much to the relational model from a theory
perspective (according to Date, who gives a thorough explanation of his
reasoning).

So, in short, learn how to program object-orientedly with an RDBMS
first, then later check its feature list to see how extra object
oriented syntax might make things easier for you. Fundamentally, RDBMSs
and ORDBMSs have the same capabilities.

Regards,
    Jeff Davis