Re: Sixth normal form

On Aug 19, 1:43 pm, "Brian Selzer" <br..._at_selzer-software.com> wrote:
> "paul c" <toledobythe..._at_oohay.ac> wrote in message
>
> news:%CNxi.70306$fJ5.3346_at_pd7urf1no...
>
> > JOG wrote:
> >> ...
> >> Does anyone else understand any of this? ...
>
> > It strikes me as absurdly technocratic, no apparent value, ie. for me the
> > answer is no. I don't see any value in theory for its own sake unless you
> > can say or guess at *some* point along the way what the "sake" is.
>
> [snip]
>
> No apparent value.... I gave an example before, but perhaps it was a bit
> too complicated. Suppose that you have a 5NF relation schema,
>
> employee {emp#, last, first, ssn, payrate} where emp# is the key, last is
> the last name, and first is the first name, ssn is the social security
> account number and payrate is the hourly pay rate.
>
> Now split it into the family of 6NF schemata,
>
> emplast {emp#, last}
> empfirst {emp#, first}
> empssn {emp#, ssn}
> emppayrate {emp#, payrate}
>
> Wouldn't it be a bit strange for an employee to have a first name but not a
> last name?

Yes it would be strange if a person had no surname. Would be strange that there is no proposition containing a person's last name. No. In the RealWorld(tm) its always possible there we will be missing info. See the difference?

> How about a pay rate without a social security account number?
> Under the domain closure assumption, if there is a value for emp#, then
> there is an employee with that employee number. For example, if there is a
> tuple {emp#:152, first:Brian} in empfirst, then there is an employee with
> employee number 152, and that employee has the first name, Brian. Under the
> closed world assumption, the absence of a tuple with employee number 152 in
> emplast indicates that the employee with employee number 152 has no last
> name.

I disagree, it does not mean at all that employee 152 has no last name. Under CWA in a data model, it means there is no proposition describing that information. The first order objects are propositions, not people. A subtle but invaluable distinction.

> So how can you determine how much to pay him without a pay rate? How
> can you produce a check to pay him without a last name? How can you report
> to the government how much he was paid without a social security account
> number. If you can't pay him, then is he really an employee?
>
> I now ask what is wrong with exploring why this can happen? Is this really
> theory for theory's sake? In order to find a correct solution, isn't it
> necessary to find the root cause?
>
> I could be wrong, but I think I may have found the root cause. I offered it
> up here in this forum--the database theory newsgroup. If you don't
> understand what I'm trying to say, then please ask for clarification. If
> you see a problem with my argument, or even better, if you can prove that
> I'm wrong, then by all means do it: I'm not afraid to be wrong and would
> prefer to be corrected so I don't waste any more time on it.

I don't think it is ever a waste of time to explore these issues.

>
> > When the foundation is nothing more than mysticism, arbitrary vocabulary
> > and name dropping, any result no matter how ostensibly it appears to be
> > reasoned is likely to be up for grabs.
>
> Are you saying the foundation of the relational model is mysticism? The
> whole notion of keys is semantic in nature: does that mean that the model is
> based upon mysticism?

No, again I disagree 100%. Keys are not semantic in nature whatsoever. They are the antecedents of any material implication in a statement of FOL. Semantics or 'meaning' are added by the user at the conceptual layer, as they are to any role or value.

> The entirety of normalization theory is semantically
> oriented, does that mean that it is all founded upon mysticism?
>
> [snip]
Received on Sun Aug 19 2007 - 15:52:26 CEST