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Re: why hierarchy?

From: Marshall <marshall.spight_at_gmail.com>
Date: 26 Jul 2006 08:30:34 -0700
Message-ID: <1153927834.154804.13220@75g2000cwc.googlegroups.com>


Neo wrote:

>

> Could someone demonstrate the advantages of XML or RM at representing
> the simple example shown at www.dbfordummies.com/example/ex007.asp
> This example represents John and Mary in two hierarchies (without
> redundancy). In the first hierarchy, John and Mary are children of Adam
> and Eve who are children of God. In the second hierarchy, John and Mary
> are part of Mars and Venus respectively which are part of the Universe.

No, I don't think anyone will. You've used up quite a good deal of good will.

If you wish to proceed in your endevour, I would propose that it is your job to do these comparisons. Learn SQL well enough to write credible DDL, queries, and DML. Construct examples drawn from the real world. If you have insufficient experience to do so, find respected books and draw your examples from them. (Although I have noticed the quality of your examples improving over time, you still regularly lapse back into meaningless ones like the above.)

Once you have done so, you can construct queries yourself, in SQL and your language, and you can compare them.

> To verify which method's underlying data model is more general, one can
> observe the impact on existing schema/data/query when meeting future
> unknown data requirements (to be proposed by someone else).

You first have to have a definition of generality. As I understand the term, the SQL data model is fully general, as is the RM. If you care specifically about change management, you need to come up with a framework for describing the different kinds of changes. Then you can compare what the effect is of each kind of change.

Since you seem to be proposing not using a schema at all, you have to show what the downside of that is as well as the upside. Think typos.

And as you construct these examples, you have to do as good a job as possible with the SQL part. Everyone will assume you're using your own designs well; if you don't do a great job with the thing you are contrasting with, everyone will assume you are just making a bogus comparison.

Marshall Received on Wed Jul 26 2006 - 10:30:34 CDT

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