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Re: Normalisation

From: VC <>
Date: Wed, 13 Jul 2005 21:28:20 -0400
Message-ID: <>

"Jan Hidders" <> wrote in message news:E9gBe.144135$

> VC wrote:

>> "Jan Hidders" <> wrote in message
>> news:%reBe.144048$
>>>VC wrote:
>>>>"Jan Hidders" <> wrote in message
>>>>>VC wrote:
>>>>>>"Jan Hidders" <> wrote in message
>>>>>>>Ah, but now you are using the domain or relations, right? There is a
>>>>>>>problem with that domain. It doesn't exist. The collection of all
>>>>>>>relations is a proper class, and not a set, but domains have to be
>>>>>>The collection of all relations is most certainly a set, and
>>>>>>therefore, a domain, domain being a synonym of set. The term "proper
>>>>>>class" implies that you talk in terms of set theory other than ZF (
>>>>>>Zermelo - Fraenkel ) ). There is no need to do so for the reltional
>>>>>>model unless you can show there is ;)
>>>>>There is indeed no such need, unless of course you want to define the
>>>>>domain of relations, which you cannot do in ZF.
>>>> The onus of proof of such impossibility is squarely on your shoulders.
>>>> Please oblige (define a collection/domain of relations, within ZF,
>>>> which ain't a set).
>>>Defining a collection of relations within ZF that is not a set, is
>>>neither here nor there.
>> I am sorry but your response does not make any sense whatsoever. What
>> is "neither here nor there" supposed to mean ?
> It means that it is irrelevant for the question whether you can define the 
> domain of relations in ZF. Note that is says "the domain" and not "a 
> domain".

I am sorry but you are still not making sense. What sacred meaning does the definite article impart to a reader ? What is "the domain of relations" ? Do you mean the domain of all the relations there are ? Or some other "the domain" ?

Let's assume "the domain of relations" stands for a collection of all the relations there are.
Now, we all know, don't we, that a relation in the relational model is just a set (forgetting about the "header" which is not important). So, given that relations, or all the relations there are, are just sets, why the domain, or the collection of all the relations which are guaranteed by definion to be sets formed at an earlier [than our domain] stage in the cumulative hierarchy, is not a set ?

> -- Jan Hidders Received on Wed Jul 13 2005 - 20:28:20 CDT

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