Re: Few confusing things about first normal form

On Oct 23, 4:59 am, paul c <toledobythe..._at_oohay.ac> wrote:
> Sru..._at_gmail.com wrote:
> > greetings
>
> > 1) For DB to be in 1NF there must be no multi-valued attributes, and
> > no repeating groups. When so, data is said to be atomic. ...
>
> When Codd first used the word "atomic", he may have intended it very
> casually, as some of his intended audience were decision-makers, but
> (just as they often are today) many of those were non-technical people.
> It seems he was very much aware that no matter how good his idea was, it
> still needed to be sold.
>
> CJ Date and like-minded people have discarded the term "atomic", saying
> it is at least imprecise and at worst meaningless as far as a Codd-ian
> relation is concerned.
>
> They now like to use a more mathematical term - scalar. In their
> approach, in a the kind of relation Codd had in mind, the values of
> attributes are inherently scalar values. But many authors still natter
> on about atomic attributes. Maybe they are the kin of the 1960's
> secondary school teachers who were told to teach math from a set-theory
> perspective, never having been taught the latter themselves.
>
> Anyway, Date and company's attitude might make one wonder if 2NF should
> be called 1NF, et cetera.
>
> They discount "repeating groups" as well. As far as I can tell for the
> same reason. When Codd wrote his first papers, several hierarchical
> dbms's of the day as well as lower-level access methods had built-in
> support for such constructs. In fact I seem to remember that support
> had even found its way into Ansi Cobol. In his 1970 paper, Codd went
> out of his way to show that such a construct was redundant and therefore
> unnecessary.
>
> Many in this camp also acknowledge the logical possibility of RVA's,
> relation-valued-attributes, at the same time as saying that the
> practical need for RVA's is rare.
>
> Over the last hundred years or so, even the notion of atomic as being
> indivisible that physicists used has wandered, not just because it was
> discovered that atoms could be divided but also as more fundamental
> particles were discovered. Even before then, some had surmised that
> electrons might be jumping from atom to atom. Somewhere Date makes the
> point that data whose organization is expected to endure should be
> stored using durable principles. If the same goes for the lingo used, a
> mathematical noun/adjective seems better suited than a word like atomic
> that has so many nuances in common language.

Is the value of an attribute that is an RVA a scalar? Received on Thu Oct 23 2008 - 04:39:57 CEST