Re: Another view on analysis and ER

From: rpost <>
Date: Wed, 12 Dec 2007 20:32:39 +0100
Message-ID: <1cc24$47603757$839b4533$>

JOG wrote:


>> >So why on earth would /anyone/ want to drop step 3? I'm at a loss as
>> >to why certain cdt'ers (who are clearly intelligent people) seem to be
>> >advocating this. An absolute loss I tell you.
>> Being new here, I have no idea whom you're referring to.
>> You'll never see *me* omit step 3, But I don't buy your "neutral".
>As far as I understand OODBMS, they do drop that step 3, because they
>directly translate a single conceptual model into an identical logical
>one. In general, I think much of our conversation has probably crossed
>in the mist anyhow Reinier. I'm thinking of it as a 'lack of beer'
>issue, in that if we were discussing it at the pub, instead of on
>usenet, there probably wouldn't be any confusion ;)

Yes, I've seen that advertised as the whole point of having OODBMSes: the database would act as a more or less transparent object model "persister". (Just like XML databases, which persist XML documents.) This implies a pretty drastic change to the nature of the relationship between database and application, but I'm not convinced it's always bad to do things that way.

Moreover, an OODBMS doesn't force you to omit step 3.

Finally, an OODBMS was never the reason for my defense of ER modelling in the first place. My reason is not wanting to skip steps 1 and 2!

| 1) initial analysis of business processes and important concepts.
| 2) Formulation of an initial conceptual model (that is necessarily
| slanted to a certain viewpoint of the UoD).
| 3) Translation into a nicely normalized logical model, that's query
| neutral.
| 4) On demand, extract data back out from the neutral logical model,
| shaping it either the original conceptual view, or other conceptual
| views as needs arise from new applications.

If we take steps 1 and 2 seriously, we'd better have a decent formalism to denote and reason about their (intermediate and final) results, and ER modelling fits the bill rather well, which should be little surprise considering that everybody already uses it for that purpose.

So I don't really see any disagreement between our positions.


>But welcome to cdt. It can get rawkus in here, [...]

So I've noticed :) That's OK.

Received on Wed Dec 12 2007 - 20:32:39 CET

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