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Re: The wisdom of the object mentors

From: Bart Wakker <bhawa_at_web.de>
Date: Tue, 27 Jun 2006 00:06:13 +0200
Message-ID: <878xnj7esq.fsf@bhawa.web.de>


frebe73_at_gmail.com writes:

>> Changes to applications
>> have much to do with behavior and formatting, and not so much to do
>> with data.
>
> If we change the data, lets say we add a new column, phoneno, to the
> customer table, doesn't the application need to change?

Not all applications using the customer table may need to use each column of the table, so: not necessarily.

>
>> Since the forces that change databases and applications are
>> different, and their customers are different, they should be
>> designed for these different environments and constraints.
>
> What are the forces to change databases that would not also force
> you to change the application?

One of the applications using the same database may be the force to change the database, while the other applications may not be. Or even the idea to historize data for future use without immediate need to use in an application at this point in time.

>> If, on the other hand, the applications are designed to be independent
>> of the database structure, then the applications can use whatever data
>> structures are appropriate for their algorithms.
>
> A algorithm could must obviously know about the data structure.

Not at all! I'm currently writing many algorithms that get their data passed in as java objects. The algorithm does not need to know where the data came from and how it is stored in the database.

It is very nice that I can test my algorithms by feeding it all kinds of data that do not need to come from the database. Some of the algorithms are used with local data (fed and the output is written back), but also with remote data when called through corba. I am very happy that my algorithms don't know at all the original data structures. Of course they have some data structures private to them internally. Received on Mon Jun 26 2006 - 17:06:13 CDT

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