# Re: Normalisation

From: Jan Hidders <jan.hidders_at_REMOVETHIS.pandora.be>

Date: Wed, 13 Jul 2005 20:03:07 GMT

Message-ID: <%reBe.144048$9f4.7479324_at_phobos.telenet-ops.be>

>>>"Jan Hidders" <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message

Date: Wed, 13 Jul 2005 20:03:07 GMT

Message-ID: <%reBe.144048$9f4.7479324_at_phobos.telenet-ops.be>

> "Jan Hidders" <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message > news:FwWAe.143403$A03.7623726_at_phobos.telenet-ops.be... >

*>>VC wrote:**>>*>>>"Jan Hidders" <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message

*>>>news:AyVye.138732$g63.7370802_at_phobos.telenet-ops.be...**>>>[...]**>>>**>>>**>>>>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 sets.**>>>**>>> 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.

- Jan Hidders