Re: object oriented vs object relational
Date: Wed, 29 May 2002 15:49:55 +0200
David McCarthy wrote:
> Would someone please explain to me the difference between a
> object-oriented data base model and an object relational database model?
there is a wide range of products that call themselves "object databases" or "object-relational databases" and in some cases the marketing term has very little to do with the technology.
Looking at the "typical" representatives, I would describe the principal differences as follows:
- powerful query language, typically SQL with possible extensions for "object" capabilites
- no automatic association between objects in the programming language and "objects" in the database. You have to write your own insert and update code.
- no tables, objects are stored directly
- weak querying functionality
- very tight association between objects in the programming language and objects in the database. Most systems monitor the objects that are loaded from the persistent storage to be able to perform updates automatically.
To sum it up as simple as possible:
Object databases provide you with far better capabilities to store objects and to navigate through them. They will save you a lot of implementation work and they will provide excellent performance for this task.
Object-Relational databases will provide you with better querying functionality.
There are quite a few object databases that are currently improving their querying functionality and I could imagine that we will see a wide support of SQL at some time in the future.
> I would also appreciate it, if you could point me to a reference,
> preferably on the web, that I could use to research the advantages,
> disadvantages , features, strength and market share of each.
Akmal has posted references to some very old papers but the theory has not changed dramatically in the past years.
I do not share Akmal's impression at all that object databases
are going down. I have not seen too many productive statements
from Akmal throughout the last year other than references to
links in the web and to his dusty books and papers so I doubt
that he really is in contact with practitioners. I see lots and
lots of demand for systems that map objects to tables. If the
interfaces to do so are further standardized (as JDO tries to,
not too good and not too successful, I am afraid) it will not
make a difference, whether a relational database runs behind
the interface or an object database. Object databases will
provide the better performance for the task, since the path
from object to disk is more direct, so they will continue to
catch market share for new systems.
...especially in the mobile and embedded market, where low ressource-consumption is essential.
--- Carl Rosenberger db4o - database for objects - http://www.db4o.comReceived on Wed May 29 2002 - 15:49:55 CEST