Re: Multi Valued Interface Models?

JOG wrote:
> dawn wrote:
> > Let's start here. What is your definition of a data model as in the
> > term "relational data model"? You can bounce off
> > http://www.tincat-group.com/mewsings/2006/01/naked-model.html or choose
> > your own. Once I understand your definition of this term, I will be in
> > a better position to see if I can rephrase. (I'll respond to other
> > aspects of your posting later, gotta run). --dawn
>
> Well this is the heart of the issue for me Dawn - I do not believe in a
> "naked data model".

It is not really something you need to believe in or not. I offered a definition and description. You may use the term "blorgora" or whatever for it. It is the "data model" in the phrase "relational data model." If there can be no definition of such a thing then surely there is no such thing as an RDM, but that is not my position. There is a DM that can be defined and then modified by the adjective "relational."

> Just because there is a Logical Data Model and a Conceptual Data Model
> does not mean that by dropping the prefixes we can be left with some
> pure data model.

I am working with the term "Relational Data Model" and defined these others so as not to confuse their use of the term "Data Model" with the "Data Model" being defined.

> I understand your argument here, but it appeals to the
> logic of human naming semantics, which can be a very misleading path.

Again, if you want to take the definition and put a different term there, so be it. We can call it the Relational Blorgora and then define Blorgora as Codd defined Data Model.

> A conceptual data model, a logical data model and a physical data model
> have practically nothing in common

I used those terms to try to indicate that we are not to confuse "Data Model" with them.

> and I don't believe there is much
> correspondence to extract from them that is the "data model" component.

I did not extract it from those terms, but from RDM.

> Conceptual and logical deal in information, but physical does not, it
> only works on data. Conceptual utilises human interpretation upon
> general abstractions, logical requires formal operators on well defined
> domains.

Again, I described those in order to keep from getting them confused with the def of Data Model as in RDM.

> There is no pure semantic meaning to "data model", and the
> term's use is completely contextual.

Which is why I defined/described it only as the DM in RDM and not the others. If DM means nothing, then RDM means nothing and I don't think that is your stance, is it?

> On top of this (as I mentioned in a followup to the blog), the term
> "data model" itself is rather non-sensical. Data is nothing more than a
> one or a zero, a groove in a record, a bead moved down an abacus.

You will see I defined "data" for our purposes in data modeling differently than this. If you want to call it Oompa modeling instead, then I gave the def of an Oompa as used in the phrase Relational Oompa Modeling. In other words, you may work wtih the definitions given and not the terms if they are distracting.

> How
> on earth can such an abstract nugget of nothingness ever be "modelled"?

That is not the def of data in play here. I'm working with Date's "data are facts" or, in my case so as not to confuse people "accurate data are facts."

>
> In my eyes, the term should be "information model",

That's fine -- use different terms, but the same meaning and you should get to the same spot.

> and if it was we'd
> start to lose the confusion between layers. Consider a team developing
> a game's engine with a physics model. They distinguish the model and
> its encoding, not some "logical" physics model and the "physical"
> physics model. That sort of terminology would seem daft to them - we
> are just unfortunately used to it here.

I'll buy that, but it doesn't change my argument.

> Now if you are defining a new meaning for "data model" that corresponds
> to an interface that is fine

No, I am contending that is what Codd's def of data model is about. It is all about the representation of the data at the interface point between a client of a database and a database service.

> - but it is certainly not a logical data

No, I tried to be clear that the terms conceptual, logical, and physical data models were not the "data model" as in relational data model.

> model (as you acknowledge) as we use the term normally, and so
> comparing it to the RM is like comparing apples and pears in my book.
>
> All best, Jim.

It sounds like the terms are messing with you. You may use variable names or any words you like for the concepts, but the definitions should lead you to the same point.

Cheers! --dawn Received on Tue Feb 14 2006 - 02:13:45 CET