Re: Multiple-Attribute Keys and 1NF

On Aug 30, 12:50 am, mAsterdam <mAster..._at_vrijdag.org> wrote:
> 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.

Ok, well the wire example was just that - a contrived example, and as it turns out not a particularly good one given that I can hardly argue against the fact that wire patterns are codes, and I can't really imagine why anyone would be interested in splitting them up into constituent colours (perhaps for an investigation of colour-blindness? Tenous).

Another example that occured to me in the past were the propositions: Some cows have black fur and white fur.
Some cows have brown fur.
Some cows have red fur.

Its exactly the same example in structure, but it is a lot harder (for me) to be comfortable with a 'code' view of the repeating roles. (and yup, again in RM I would use two relations and a surrogate for this, as opposed to an rva). Is everyone else still comfortable with a code interpretation? Dank je wel, J.

> The purpose here is: don't get electrocuted because of
> not knowing which wire is live. I am not kidding :-)

When I first did any electrics I both managed to put a floorboard nail through the main circuit, and within an hour take a circular saw through the lighting circuit. I've been infinitely more careful since.

>
> >>> 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 - 12:52:48 CEST