Re: Multiple-Attribute Keys and 1NF

David Cressey schreef:
> 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.

Dense? Electrocuted!

> 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.

No. Please do not dive into the subleties just because they are there. It is code - nothing else. That the symbols are colors, not characters as we are more used to, does not change the essence of the example.

> 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.

Because it is code, the colors as such are irrelevant.

> 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?

I do, but does Jim? Received on Thu Aug 30 2007 - 02:06:25 CEST