Re: Mixing OO and DB

From: Patrick May <pjm_at_spe.com>
Date: Mon, 24 Mar 2008 20:01:38 -0400
Message-ID: <m27ifr4qot.fsf_at_spe.com>


mAsterdam <mAsterdam_at_vrijdag.org> writes:
> Patrick May schreef:
>> The fact that views can be used actually demonstrates that the
>> application can be decoupled from the schema.
>
> Imagine trying to provide an example to illustrate the level of
> decoupling. I think we'ld wind up with aliases to refer to a subset
> of the same data the schema describes - or are you talking about
> more radical decoupling?

     If the application implements the solution using a DAG, for example, and the state of each node in the DAG is stored in a relational database, then a mapping between the two models must take place. If the application changes the way it uses its internal model, that shouldn't have an impact on the schema. If the schema is changed but still provides sufficient data, albeit possibly in a different form, to instantiate the DAG nodes, that shouldn't impact the application logic. Only the mechanism that provides the decoupling between the two, typically an ORM layer, needs to change in a well designed system.

>> application can be decoupled from the schema. You are suggesting
>> using views to do so. That's one possible mechanism. OO languages
>> provide others.
>
> Which?

     ORM tools, DAOs, and caches, for example.

Sincerely,

Patrick



S P Engineering, Inc. | Large scale, mission-critical, distributed OO
                       | systems design and implementation.
          pjm_at_spe.com  | (C++, Java, Common Lisp, Jini, middleware, SOA)
Received on Tue Mar 25 2008 - 01:01:38 CET

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