Re: Database type independence
From: Dagfinn Reiersol (reiersol_at_online.no)
Date: 08/23/04
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Date: Mon, 23 Aug 2004 08:37:12 +0200
Fredrik Bertilsson wrote:
> Many OO evengalists argue very hard for making the persistance layer
> independent of the database type (RDB, OODB, LDAP, etc). They want to
> be able to change the database from a RDB to an OODB without changing
> the business logic.
>
> But the cost for doing this is very high.
I don't think that's necessarily the case. In my experience, once you've
made a persistence layer that's independent of SQL, the interface
naturally tends to be independent of database type as well.
>The developer is forced to
> implement (or configure) an extra transformation/mapping layer. The
> persistance frameworks becomes unnecessary complex. This requirement
> about database type independance is one of the main reasons that EJB
> is so very complex. Besides, data-aware components are not possible to
> use because of this requirement.
>
> My question is, is it really worth the cost to make the architecture
> independant of database type. On the software market, there are a huge
> demand for relational database vendor independant applications. Most
> customers want to be able to run the applications they buy on their
> favorite dbms system like Oracle, SQL Server, MySQL etc. But how many
> customers want the application to be able to run on their OODB? I have
> never heard about it anyway.
>
> Relational databases have proven to be the superior database type.
> They have almost 100% percent market share and this fact does not seem
> to change in the near future. In fact relational databases is more
> likely to live longer than most programming languages used today
> (Java, C#, C++, PHP, VB etc). There have been numerous examples of
> applications changing programming languages (from Cobol and Fortran to
> Java or VB/C#) and the database remains the same. But the examples of
> changing database type and keeping the application the same is
> extremely few.
>
> Is it really reasonable to invest money in a feature (database type
> independence) that in almost no cases are needed? I think that if IT
> managers really knew that when they are investing in mainstream OO
> architecture, they are also spending money on things they will never
> need, they would make different decisions.
>
> It would be interesting if it is someone out there that actually uses
> something else but relational databases for persistance? And in that
> case, what type of applications and what database vendor. It would be
> even more interesting to know if someone actually have changed from
> relational database to OO database (or something else), whithout
> having to rewrite the business logic.
>
> /Fredrik
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