Re: We claim that delete anomality is due to table not being in 3NF, but...
From: paul c <toledobythesea_at_oohay.ac>
Date: Fri, 31 Oct 2008 03:05:58 GMT
Message-ID: <qCuOk.5245$fF3.2496_at_edtnps83>
>
> Hi Paul,
>
> This is cdt, not alt.philosophy. I was not after an existential
> discussion on absolute reality. :)
>
> You're reading way more into my example than I intended. The point I
> tried to make is that functional dependencies are not determined by what
> is or is not stored in the database, but by how entities and their
> interactions in reality. The DB is a model of reality and changing the
> model won't change reality.
>
> I already considered the example pretty bad when I wrote it, and now
> that I see what you read into it, I'm really embarassed...
>
> Best, Hugo
Date: Fri, 31 Oct 2008 03:05:58 GMT
Message-ID: <qCuOk.5245$fF3.2496_at_edtnps83>
Hugo Kornelis wrote:
> On Wed, 29 Oct 2008 22:59:25 GMT, paul c wrote:
>
>> Hugo Kornelis wrote: >> ... >>> Functional dependencies stem from reality. Whether or not you choose to >>> include B in your model does not change the situation where, apparently, >>> C depends on A through some intermediary B (that is not in the DB). >>> >>> In a DB that stores PersonID and EyeColour, one might argue that the >>> actual dependency goes back to the parents of the person and their >>> genetic patterns - but those will typically not be stored, and yet the >>> EyeColour still depends on PersonID. >>> ... >> >> Assuming you're saying it's improper to depend on any notion of absolute >> reality, I think I'd agree. Doesn't a db aimed toward aiding some >> present function necessarily stand for a very fractional/partial (or >> even distorted) reality? Eg., if it's not fractional it's probably >> unwieldy and untoward. Seems to me that the EyeColour dependency hints >> at this - when the purpose of a particular set of tables isn't concerned >> with dna, one likely ignores blood lines. Further, I suspect that no db >> ought to introduce fd's that aren't patently implicit in the user's >> requirements/biz rules/application intent. In the USA, I gather that an >> address that is complete enough for a mailman to deliver to, along with >> a city and a state will determine zipcode, yet I suspect there are many >> tables in non-postal db's that have a column set such as (Customer, >> unit, streetaddress, city, state, zip).
>
> Hi Paul,
>
> This is cdt, not alt.philosophy. I was not after an existential
> discussion on absolute reality. :)
>
> You're reading way more into my example than I intended. The point I
> tried to make is that functional dependencies are not determined by what
> is or is not stored in the database, but by how entities and their
> interactions in reality. The DB is a model of reality and changing the
> model won't change reality.
>
> I already considered the example pretty bad when I wrote it, and now
> that I see what you read into it, I'm really embarassed...
>
> Best, Hugo
Sorry Hugo, consider it my fault entirely. In order to keep my reason short, I'll just blame it on the grape. Maybe one day, I'll figure out a way to put it better than I did.
best,
p
Received on Fri Oct 31 2008 - 04:05:58 CET