Re: One-To-One Relationships

From: rpost <>
Date: Thu, 06 Dec 2007 21:12:11 +0100
Message-ID: <f1027$4758579b$839b4533$>

JOG wrote:

>[...] Ugh, that's even worse than a logical model based on ERM. Ah yes the
>OO-data model, the very one that died on its ass because it was a
>nightmare to query,

Duh. Of course it isn't easy to query; that's what relational models are for. It's a compromise. But it supports relational models.

>nevermind the fact it was a retro-grade
>reinvention of the network model that was superceded 30 years ago.

The network model didn't have query at all, as far as I recall.

>> > We can only ever
>> >identify things from observable attributes (and refer to them by
>> >attributes too!).
>> Certainly, but we don't always make those attributes explicit.
>Yes we do. Always.

Not in my experience.

>> And we don't always know what the relevant identifying attributes are.
>Yes we do, otherwise we can't identify them in the real world.

You mean, assuming that we can identify them consistently throughout the lifetime of the model. This is getting repetitive.


>> Should I ever want to, let's say, meet you on IRC or over coffee, I'd need
>> to extend my model of you, and provide a more detailed identification.
>Nope, then you'd be dealing with a different entity.

It depends on who you ask.


>> Please describe how you describe that persons are heads of departments
>> in a way that doesn't predetermine how I'm going to identify persons
>> and departments from now on. Or is it Just Wrong to want that? Why?
>Well not just wrong, but nonsensical. How can you describe something
>if you can't identify it? C'mon Reinier!

I didn't say I can't identify it. I'm just saying I may not yet have determined how to identify it, or that I want to identify it differently tomorrow. This is getting repetitive.

>> >> Does that mean
>> >> we should express the meaning of that statement, the "head of department"
>> >> relationship, as one between department names and person names?
>> >Why not? Its just data. Whatever conceptual model we want to conjure
>> >in our heads afterwards is our own business.
>> Nope. We don't decide whether people change their names,
>> the personnel administration does (where I work, at least).
>> We don't want an administration with headless departments
>> as a side effect of name changes.
>I'm afraid you've missed the point. I've given you examples but I'm
>not sure you have digested them properly mate.

The feeling is mutual. This is getting repetitive. Thanks for the effort anyway; I still learnt some things.


>I can only reccommend you go off and read all the arguments against
>the disaster that has been OO-DBMS.


Received on Thu Dec 06 2007 - 21:12:11 CET

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