Re: Multiple-Attribute Keys and 1NF
Date: Thu, 30 Aug 2007 01:50:10 +0200
Message-ID: <46d60611$0$242$e4fe514c_at_news.xs4all.nl>
JOG schreef:
> mAsterdam wrote:
>> JOG wrote: >>> I am still fighting with the theoretical underpinning for 1NF. >> My answer won't help you in that quest, sorry. >> I like the example, but I don't think it illustrates a NF problem. >> Yet I like it because I think it illustrates a much more basic, >> non-formal issue. >> >>> As such, any comments would be greatfully accepted. >>> The reason for my concern is that there >>> /seems/ instances where 1NF is insufficient. An >>> example occurred to me while I was wiring up a dimmer switch (at the >>> behest of mrs. JOG, to whom there may only be obeyance). Now I don't >>> know the situation in the US, but in the UK a while back the colour >>> codes for domestic main circuit wiring changed. Naturally the two >>> schemes exist in tandem, as exhibited in every house I've had the joy >>> of doing some DIY in: >>> Brown -> live. >>> Red -> live >>> Blue -> neutral. >>> Black -> neutral. >>> Green and yellow -> earth. >> This is dictionary of a little language. >> left of the '->' is the code, to the right of it is the explanation. >> The code is expressed with colors as symbols, >> just as in our phonographic latin the words are expressed >> with soundsymbols. A color-alphabet. The codes are not colors as such. >> Your information need is the code explanation, not >> anything about the colors.
>
> Confuscious, he say mAsterdam, he wise ;)
>
> I wholly agree that any encoding is biased to a certain expected
> information need. However I have always worked on the principle that
> in a theoretical model I want to minimize this query bias as much as
> feasibly possible (and therein lies the strength of the RM over other
> approaches). Consequently In this instance I see what one can gain by
> encoding "Green" and "Yellow" separately in terms of flexibility, but
> not what one would lose. Either way, I am willing for the example to
> be interpreted in terms of such an information need.
The example has an existence of its own, though.
Your preferred interpretation requires a leap of faith many mediocre math-inclined formalists show willing to take over and over again to no avail.
Whenever modeling, one should keep focus as to what is being modeled and what the purpose of the model is. The purpose here is: don't get electrocuted because of not knowing which wire is live. I am not kidding :-)
>>> The issue with encoding these propositions is that the candidate key >>> for each proposition may consist of one _or_ two colours. >> This is similar to asking how many characters can make up a >> word or how many words a sentence.
>
> I was intending to describe of an item that is identified by two
> attributes which play the same role. Just knowing this might be
> desirable /I think/ validates the example.
Mostly, yes, agreed. However colors simply do not have a role, here. Symbols are /not/ roles (ok, ok, except for the trivial/desubstanced role of /being/ a symbol).
> What I am really struggling with is whether requirement of a surrogate
> key to achieve the information need (as a result of enforcing 1NF) has
> a theoretical basis. Is 1NF just there to provide a structure that
> fits a relation, or does it have a deeper purpose that I haven't yet
> grokked.
The need is a intersubjective topic /ergo/ not formal.
>>> Now I have a couple of options, none of which seem satisfactory.
[snip]
This is because you desire from form(alisms) that which it by its nature cannot provide: substance. Received on Thu Aug 30 2007 - 01:50:10 CEST