Re: Normalization by Composing, not just Decomposing
From: Jan Hidders <jan.hidders_at_REMOVETHIS.pandora.be>
Date: Tue, 13 Apr 2004 19:54:04 GMT
Message-ID: <wzXec.70525$217.4583518_at_phobos.telenet-ops.be>
>
> [Date's 6NF]
>
>
> Could you share some of the controversy?
>
> That is, only when you exclude intervals as key-attributes.
> When you allow intervals as key-attributes (and... why not?)
> it maps to 6NF.
Date: Tue, 13 Apr 2004 19:54:04 GMT
Message-ID: <wzXec.70525$217.4583518_at_phobos.telenet-ops.be>
mAsterdam wrote:
> Jan Hidders wrote:
>> mAsterdam wrote:
>
> [Date's 6NF]
>
>> It's not uncontroversial, by the way.
>
> Could you share some of the controversy?
>> ... Actually finding out what the elementary facts are is essentially >> the same as normalizing to 5NF.
>
> That is, only when you exclude intervals as key-attributes.
> When you allow intervals as key-attributes (and... why not?)
> it maps to 6NF.
> My take is that Date, Darwen and Lorenzos formulated 6NF the way they
> did to make it fairly obvious that 6NF is more strict than PJNF (5NF)
> (i.o.w. that every set of relations (relational variables) in 6NF is by
> definition also in 5NF so 6NF is another step on the lossless
> decomposition ladder). However, until I see an counterexample -
> preferably pizza orders related - I'll look at 6NF as an alternative
> predicate for the INF, the irreducable normal form (loose definition:
> just one non-key attribute) (BTW great
> acronym, don't you think? :-).
I wonder if Date et al. have realized that.
- Jan Hidders