On Jan 26, 3:19 am, Sylvain Hellegouarch <[EMAIL PROTECTED]> wrote:
>I think offering the use of OODBMS would be a good idea if their state
> was in a better shape. Having a storage like Durus is a good thing but
> is it enough? Do you have any standard query language?
Sorry if this ends up being a double post.
Object oriented databases don't need a standard query language. That's
right they don't need a query language. I know this may sound strange
for all those people you have this believe that a database can only be
a database if it acts like a relational database but that belief is
just plain wrong.
I want to make sure that before I continue that you know that I'm not
against relational databases. I just prefer to use the right type of
database for a given project. Sometimes a relational database is the
right one for a project but in other times an object oriented one is
the right fit. The problem is that most people are only aware of
relational databases and just use them as that's all they know. If
they do try an object orient database it's usually after using a
relational database and then they can't understand why it doesn't have
a query language. They end up feeling like a fish out of water and
come to the conclusion that OO databases are useless.
Now sometimes people end up using relational databases for the wrong
type of projects. When the do so they end up struggling with
performance issues of have to write an amazing amount of code or very
complex queries in order to successfully use the database for the
project.
Over the years relational databases become more and more complicated in
order to handle these projects that don't fit well with relational
databases. They add these complexities so that they can continue to
sell their kool-aid that relational databases are the King of databases
and that can handle all you persistent storage needs.
Another problem is created by ORMs. ORMs try to solve the impedance
mismatch that exists between object orient programming and relational
databases. Now don't get me wrong, ORMs are great for projects that
are a good fit for relational databases as they bridge the gap build
between the OO code and the database. The issue with ORMs is that it
makes it easier to connect OO code with the relational database that
some applications that would be so difficult to connect to a relational
database become possible. So you end up with applications that would
be a natural fit for an OO database doing all kind of abuse to a
relational database.
To be able to use an OO database effectively requires that you have
good skills in creating object orient code. Unfortunately there are
not many people who create good object orient code as it takes time to
acquire the skills. Most people just don't have the patience to learn
the skills or have no idea how much more effective they would become
when they master the skills. If they knew what they were missing they
would likely make the effort.
Anyway, lets say you want to build an OO app that does not have the
need to store data persistently. If you had an object of type Oa that
had a attribute called obs that was a list that contained objects of
type Ob. So you end up having a one to many relationship between Oa
and Ob classes. Would you need a query language when you have a
reference to an Oa object and would like to iterate the Ob objects that
are linked to the obs attribute? I don't think so. Now this is just a
simple example but I hope you start to understand why an OO database
doesn't require a query language.
Now OO databases are not for all projects. OO databases would be a bad
choice if you have projects that are written in different languages
that need access to the same data. They are also a bad choice when an
application needs to be able to perform complex and ad-hoc searches
over the data. Now don't be fooled by that last statement. Many times
people think they need the flexibility in querying that a relational
database offers but quite often that is not the case. If you end up
creating relational databases with many tables that have many fields
but only find yourself querying on only one or two fields and rarely
need to perform an ad-hoc query, as you already know all the possible
queries you may need, I would say you chose the wrong type of database.
Hopefully this makes some sense and just maybe a few of you we see the
light and start to recognize when to use an OO database over a
relational one. Using the right tool for the job can make a really big
difference.
John
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