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Re: normalization problems

From: David Cressey <david_at_dcressey.com>
Date: Fri, 22 Dec 2000 13:41:08 GMT
Message-ID: <URI06.231$2X4.18223@petpeeve.ziplink.net>

Vaughan,

I've seen the kind of approach you outlined to Karen, in a large application in the
field. My reaction is more on the practical level than on theoretical level.

An approach like the one shown in the Category Attribute table has its plusses and minuses. The plusses are that it does indeed solve the problem that Karen outlined, if I read her correctly. And it's OK on performance.

It also allows new relationships to be encoded by adding new rows to the Category Attribute table without altering the schema. From the point of view of the programmers, this is a plus, because now they can implement relationships that they discover on the fly, without waiting for a DBA to approve a schema change.

From my point of view, however, allowing undocumented relationships to be stored in a database undermines the purpose of having a schema to begin with.

If you do that, and if you expect the result to be as useable by a database expert who comes on board, then you have to go through the task of documenting all the relationships that are implemented in the Category Attributes table. If you don't then the data in the database will become mysterious and unworkable just as fast as it once did in the days of files, before databases came along.

In the case I saw, the only people who understood the data were the programmers. It cost a lot of effort, and a lot of money, to rediscover the relationships in the data.

It's a trade off.

Vaughan Powell wrote in message <91vcfl$vtc$1_at_nnrp1.deja.com>...

>This is just a 'get you started' suggestion, not a complete database
>design - you will have to follow through my ideas and see if they a
>suitable for your application.
>
>You could generisise the Product Category details with the
>Category_Attribute table:
>
>Category_Code -- Primary Key
>Attribute_Code -- Primary Key - -- e.g. response_cycle_analysis
>Attribute_Type -- e.g. datetime, numeric, string
>Attribute_Label -- e.g. Response Cycle Analysis
Received on Fri Dec 22 2000 - 07:41:08 CST

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