Re: MV Keys

In article <1141222180.758766.226530_at_u72g2000cwu.googlegroups.com>, jog_at_cs.nott.ac.uk says...
> Brian Selzer wrote:
> > Doesn't the determination of whether a type is scalar or not depend upon the
> > universe of discourse? I think that a string is a scalar if any of the
> > following statements hold: (1) individual character values don't belong to
> > the universe of discourse, (2) the meaning of the individual character
> > values aren't directly augmented by the attribute name, (3) the meaning of
> > the individual character values aren't augmented by their position in the
> > list, or (4) it is only the permutation of character values that has meaning
> > with respect to the containing relation. For example, the elements in a
> > list of birth dates aren't just dates, they're birth dates; the numbers in a
> > coordinate aren't just numbers, they're longitude and lattitude. I think
> > that some of those properties could be applied to other types as well,
> > though I can't think of an example just now.

I believe this amounts to the same thing I was saying: scalarness/atomicness is subjective, depending on perspective/context.

> Some good points here. When we talk about scalars, we are not really
> talking about them in their mathematical sense (just look it up in a
> mathematical dictionary for evidence this). In actuality what one is
> talking about when one refers to scalars in this context are atomic
> values - a value that may not be broken/down into component parts.
>
> But *nothing* is atomic. Ultimately everything may be defined
> compositionally, hence the debate about Varchars, strings, deciamls,
> etc. I honestly believe this is to be a fruitless argument.
>
> In a finite system such as a database, at some point one simply HAS to
> stop decomposing, and the system is currently forced to proclaim when
> this should occur.

Why?

> Hence 1-NF refers to decomposition down to atomic datatypes *as defined
> by the system*, whether that includes strings, dates, whatever.
>
> I realise this definition sounds circular but that is the nature of
> something as artifice-laden as atomicity. Dig any further and again you
> will end up in the quagmire of epistemology, and there are no
> satisfactory or practical answers there.

Fair enough, but this renders the entire concept of 1NF useless, both in theory *and* practice.

-- 
Jon