Re: Multiple-Attribute Keys and 1NF

From: JOG <>
Date: Wed, 29 Aug 2007 13:16:22 -0000
Message-ID: <>

On Aug 29, 12:49 pm, Bob Badour <> wrote:
> JOG wrote:
> > On Aug 29, 6:10 am, "David Cressey" <> wrote:
> >>"JOG" <> wrote in message
> >>
> >>>Okay, sure. But then to be able to query for green and yellow
> >>>individually one must employ a further relation encoding two more
> >>>propositions that state "'Green and yellow' contains 'Green'" and that
> >>>"'Green and yellow' contains 'Yellow'" respectively. One then has a
> >>>schema with two domains - one for the composites and one for
> >>>individual colours (which is what I was inferring when I initially
> >>>said a new one was being added).
> >>It took me a while to realize that what you meant from your original
> >>description was that
> >>"a green and yellow wire means earth". I had thought you meant "a green
> >>wire means earth" and "a yellow wire means earth". Pardon me for being
> >>dense.
> >>Clearly what we have here is not a domain of colors, but a domain of color
> >>codes, where a color code contains one or more colors, and maybe a "thick
> >>or thin" qualifier on each color.
> >>It's not clear to me why you need to able to query on simple colors, unless
> >>you need to decompose the color coding scheme into its constituent parts for
> >>some reason.
> >>There are lot of code domains where each code is made up of a set of more
> >>primitive elements.
> >>Perhaps a very relevant one might be "character code". If I have the
> >>following primitive elements:
> >>B1, B2, B4, B8, B16, B32, B64, B128
> >>(which might be an odd way of labelling bits 0 through 7 of a byte), I can
> >>think of the character code for 'A' as being B64+B1. Now I could query on
> >>all the character codes without necessarily having an operator that would
> >>yield "all the codes that include B1".
> >>I think that the colors, as constituents of color codes, play the same role
> >>as bits, as constituents of character codes. Do you agree?
> > Yes. I mean no. No, yes. Gnngh ;)
> > Ok, of course I understand your point - a wire can be viewed as having
> > a colour code, which itself has constituent parts. But its just one
> > interpretation right. I am still seeing a difference between the
> > propositions:
> > * There is a colour-code "yellow and green" that denotes "earth".
> > * The casing of an earth wire features the colour yellow and the
> > colour green.
> > Its just like the difference between the propositions:
> > * My office is B42
> > * My office is on floor B, room 42.
> > There are instances where I may well want to encode as the second
> > proposition forms. And /if/ that were the case (iff), well 1NF is
> > precluding me from doing this in terms of the wire example.
> I disagree. You have already noted that 1NF allows this with exactly 2
> relations (or with 1 relation and one or more operations on the color
> code domain.)

True, I do see that, but it does so by requiring the invention of a colour-code concept which isn't in the proposition "The casing of an earth wire features the colour yellow and the colour green". Received on Wed Aug 29 2007 - 15:16:22 CEST

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