Re: Codd provided appropriate mathematics ... (was Re: Relational and MV (response to "foundations of relational theory"))

I agree.

"Dawn M. Wolthuis" <dwolt_at_tincat-group.com> wrote in message news:c1lktq$b6h$1_at_news.netins.net...
> "Tom Hester" <$$tom_at_metadata.com> wrote in message
> news:aff87$403e41e1$45033832$6812_at_msgid.meganewsservers.com...
> > Both are non-1NF. Codd defines first normal form in terms of simple
> > domains. That is the interpretation of a single element in a domain can
> > only be an atomic element of a set. It cannot be further decomposed.
>
> The fact that RDBMS's permit the attr1, attr2, ... approach and that these
> make for a mathematical relation with simple elements, leads me to suggest
> that this approach would not be considered multivalued. However, the fact
> that this is possible means that RDBMS data practitioners spend more time
> identifying what is different about attributes so they don't have to
create
> new tables for elements (so you get MAJOR1, MAJOR2, MAJOR3 with
> justification that the second major is really considered a second major
and
> not a third or first sometimes) rather than MAJORS[n] or an array of
majors
> (array, list, ordered or unordered set, collection, map, ...) So, at
first
> glance it is non-1NF, but you know some data modeling person somewhere is
> justifying why these are really different elements.
>
> Spending time finding patterns of similarity, rather than differences, in
> data elements can lead to considerable productivity gains -- we would do
> well to keep ourselves in the reusable pattern business with our data
> implementations as well as our "code". --dawn
>
> > "Eric Kaun" <ekaun_at_yahoo.com> wrote in message
> > news:k6r%b.50112$LX2.42031_at_newssvr33.news.prodigy.com...
> > > As an aside in this discussion, I've seen "multivalued" defined 2
> > different
> > > ways in explanations of relational (some of which are really bad).
> > >
> > > 1. Where attribute A can hold a list of values (type LIST)
> > > 2. Where there are attributes A1, A2, A3, A4 (for example), all of the
> > same
> > > type and meaning. For example, ADDR1, ADDR2, etc.
> > >
> > > Does 1NF refer to both of these? If not, what's the proper terminology
> for
> > > each of these cases?
>
>
Received on Thu Feb 26 2004 - 22:56:33 CET