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Re: Lucid statement of the MV vs RM position?

From: dawn <>
Date: 26 Apr 2006 19:14:46 -0700
Message-ID: <>

Jan Hidders wrote:
> dawn wrote:
> >
> > It is conceivable to me, Jan, that in the inner sanctum the RM is
> > already dead (or altered so much that 1NF, 3VL, and the IP understood
> > as relations and primitive scalars are all gone), in which case I'm
> > only adding my voice to what is already known by theorists. That would
> > be great as it would much better align what I have seen as best
> > practices with the theory.
> Gee, Dawn, perhaps you should write an e-mail to the friendly people at
> dbdebunk to tell them that you and they agree after all.
> Ok, now my cheek hurts. :-)

;-) You should see the responses I get when I do write dbdebunk. There are some folks that I just can't charm ;-) and I don't think a beverage and a chat in person would change that. Ah well...

> > My goals would still include getting the word out about this fatality.
> > I doubt many undergraduate courses teach that 1NF, as we knew it, is
> > dead, for example. I sure don't see that knowledge having made it into
> > the practitioners "common knowledge" as yet.
> It shouldn't.

Yes, it should. Should all XML documents be in 1NF? If not, why not?

> The "theorists" you referred to, although formally not
> opposed to nested relations, warn for using them too enthousiastically.

Yes, I know. Baby steps.

> Never mind the sloppy data modelling attitude where one forgets to
> indicate that a certain list is actually a set.

It is sloppy only if there is a business need to make the distinction. Every set whose values I've ever enumerated for anyone, either in writing or verbally, has been passed as a list ;-) I can imagine instances where this could be a problem, but it just doesn't seem to be the show stopper that some might think. I would prefer the added precision, of course.

> Finally, whether using
> nested relations / lists is in practice a good idea depends on how
> efficiently your DBMS supports them


> and for example can do decent query
> optimization on them. AFAIK the jury is still out on that one,

Well, there's more than 30 years of production apps out there running flavors of MUMPS, PICK, and others from which the jury could gather data. Even if you don't like the lack of DBMS-defined constraints on the way in, those are not required for determining read-only query performance. Unfortunately, there are no industry performance measures of which I am aware that are not designed strictly for SQL-DBMS's (or do you know of some?)

> so it is
> certainly not something that should be promoted in undergraduate
> classes as the "currently known best practices".

I guess I still have work to do, eh?

> > [...] If you do know of an implementation of lists that
> > aligns with current relational theory (which was once described as "no
> > lists" or "no repeating groups"), I'm very interested.
> AFAIK the thing you have in mind doesn't exist yet.

That's what I thought. I'll do what I can (which would be a lot easier if I were not both ignorant AND stupid, I suspect.) smiles. --dawn Received on Wed Apr 26 2006 - 21:14:46 CDT

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