Re: Lucid statement of the MV vs RM position?

dawn wrote:
Jon Heggland wrote:
dawn wrote:
For example, we model data for XML
documents for data exchange using multivalues even if we could do
otherwise.

You do? Why?

For the same reason I use a multvalued database, perhaps.

Brillant [sic].

I don't see the relationship between XML, RVAs and normalisation.
Normalisation by definition applies to relations/relvars only.

You can model an XML document with a relation, you just need
list-valued attributes and RVAs to do so.

1. A *relation*? Or do you mean a tuple in a relation?
2. No, you don't (need LVAs/RVAs). An XMLVA might be nice, though...
3. So what?

(I must
confess I haven't seen the light with regard to using XML for exchange
of data to/from relational systems either.)

But it is the relational systems that are going to change to accomodate
and there is a reason for that.

Indeed? What changes are needed, and what is the reason?

Yes, there are, but I don't see them written up anywhere. Ever since
the RM busted onto the scene, business data processing types who use
NF2 approaches seem to have gone into hiding, just going about their
business but talking only amongst themselves so as not to ruffle the RM
feathers (or something).

That's an... interesting hypothesis.

I honestly don't know why I can't find much
related the practice of data modeling in an NF2 world. That is gonna
have to change, I would think.

Good luck with that.

Isn't "modelling" "data for exchange" just producing
reports?

Output on one side, input on the other.

So? Call me old-fashioned, but if I wanted to exchange data between two
relational systems, I'd choose relations as the exchange data model.

You can think of it as
decidedly different from database data modeling until you decide you
want to persist and report on the exchange data.

Until I decide to introduce duplication, redundancy and query bias, and
report on (the contents of) my reports? Then I may be stuck in my
fossilised ways for quite some time, I fear.

In which case you do what is most convenient for the task at
hand. Which is very different from designing the database, where you (or
at least I) want it (i.e. the logical model) to be as orthogonal,
unbiased and simple as possible.

In order to model as much meaning as feasible, I want my data modeled
in a biased way (a way biased toward meaning where color and paper are
different, see chat with JOG on this topic),

"Biased towards meaning"---as opposed to what? Meaninglessness? I'm
talking about biased towards query as opposed to update, or towards
certain queries at the expense of others. Twisting reasonably accepted
terms like that does not help your argument.

FWIW, I don't endorse the entity-attribute thinking you (and JOG)
indulge in. It confuses the issue, and does not contribute anything. For
example, I consider treating colour and paper differently a flaw, not an
advantage.

Why do you want to "persist" "data for
exchange"? (I'm not really comfortable with either of those terms.)

OK, I want to store all of the transactions coming in from web
services. Is that any better? --dawn

Like a log? I still don't see where you're going, or why you think
"multivalues" are needed.
--
Jon
.

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