Re: Data Display & Modeling

"Eric Kaun" <ekaun_at_yahoo.com> wrote in message news:yeqoc.1165$qr1.246_at_newssvr32.news.prodigy.com...
> "Dawn M. Wolthuis" <dwolt_at_tincat-group.com> wrote in message
> news:c7ioke$n22$1_at_news.netins.net...
> > "Eric Kaun" <ekaun_at_yahoo.com> wrote in message
> > news:YzQmc.86$Qm5.68_at_newssvr32.news.prodigy.com...
> > > And I should add that Levene contributed to the "Nested Relational
Data
> > > Model", which I believe Date discusses in Intro-DB Systems as
> unnecessary,
> > > and proceeds to show why the basic relational model can tackle the
same
> > > problem domains without modification (and with additional benefits). I
> > can't
> > > remember the details - Dawn?
> >
> > Although Date talks about relation-valued attributes in Intro-DB, I
> haven't
> > found anything describing a nested relational model (but I've not read
all
> > the way through). Instead he adds in the GROUP and UNGROUP operators in
> D.
> > However, there are a couple of papers that you can pay for and download
> from
> > dbdebunk.com where Date discusses nested structures and asks questions
> about
> > MultiValue (PICK) systems and then by Pascal who gives reasons not to
use
> > relational-valued attributes even though they are not outside of the
scope
> > of relational theory (anymore).
>
> I have "What First Normal Form REALLY Means" here, and it's worth buying,
> even for MVers. Some salient quotes from it, chosen for shock value:

Yes, I agree it is a good read (although I haven't shared it with anyone else here in the corn fields)

> "... the notion of atomicity has no absolute meaning..." [and of course,
> atomicity is central to defining 1NF]
> "... a set like {P2, P4, P5} is no more or less decomposable by the DBMS
> than a character string is."
> "... relations are always in 1NF!"
> "It's certainly true that RVAs [relation-valued attributes] can be useful
in
> reports."
> "Domains, and therefore attributes or columns, can contain anything (any
> values, that is)."
> "... hierarchic designs usually arise from a limited perspective on the
> overall problem..."
> "... the hierarchic representation isn't suitable for all of the kinds of
> processing that we might need to do on the data."
> "You can't tell whether a given table is in 1NF just by looking at it..."
> "Supporting RVAs involves little in the way of additional learning... if
we
> were to introduce, say, arrays 'on the inside', then users would
necessarily
> have to understand arrays..."
>
> Obviously you can abuse this notion, but I thought you might enjoy this
> paper. It's certainly interesting, and not what's often argued with regard
> to 1NF.
>
> > > Not evidence of anything, except perhaps willingness to invent
novelties
> > > rather than exploiting what's already available
> >
> > Of course, that is what Codd did.
>
> True, although in my opinion he sticks closely to a very applicable and
> implementable theory. Higher-order logics are very useful, but first we
> should get our money's worth from first-order, which has a few miles left
in
> it, right?

I think it is likely good that we didn't hold back the evolution of language until we had some complex mathematical model on which to base it. We could have stuck with very simple sentences until we knew we could "handle" more.

> Relational is a fairly direct application of predicate logic
> without frills and extras, in my opinion, but I could of course be biased.

I would agree!

> Perhaps the DBs he helped replace lacked theory, and thus any theory would
> work, but I don't think that's it at all. He sticks to something simple,
and
> that's important - there are many mathematical systems that we wouldn't
> dream of using for databases, so there have to be some meta-criteria for
> selecting them. Topology? Statistics?

I hate to inject "common sense" or those deemed viable through observation (emperical data), but I'm gonna anyway.

> While applicable to systems of
> systems, I think they're out of line for business apps.

I suspect that if one works with databases for a couple of decades, one "feels" patterns that might not be easily captured and certainly might not be based on simple mathematics. I suspect that if one applied the wisdom gained from years of experience but from no written-down model and another applied a simple matematical model and they were pitted against each other, then, well you can finish the thought.
> > > and solid.
> >
> > mathematically solid or history-of-savingcompanies-big-bucks-solid?
>
> Unfortunately, many vendors could argue the same thing. Oracle, Microsoft,
> IBM, Red Hat, blah blah blah. Depends on who funds the study.

Yes, indeed unfortunate.

> But I'll agree
> with your experience and say that it sounds like your Pick systems have a
> good development environment. I still think that if I were using it, I'd
be
> using relational as my guide, and I think you do the same - it's only on
> display-only attributes where we disagree on 1NF. For that reason, I'd
> highly suggest buying the paper above (no, I have no stake in the success
of
> their web site).

I have bought both $10 papers from there -- Date's and Pascal's and I do find them worthwhile.
Cheers! --dawn Received on Wed May 12 2004 - 19:29:46 CEST