Re: Modelling Considered Harmful

Kenneth Downs wrote:
> I wonder if anybody would care to dispute the thesis that use of the term
> "modelling" with regard to databases does more harm than good.

Yes, it is a good excercise. I allready commented in some sub-threads, but you dismissed my remarks. I think there is more to this, so I chose to reply to the OP this time.

Let's dissect :-)

> The case can also be stated that databases are NOT models of reality.

They are not, agreed.

> They are rather record-keeping systems.

Yep.

> If it can be shown that databases are
> record-keeping, that record-keeping is not modelling, then it stands that
> we would not call databases models.

So far, so good.

> We need to define models and records.

Do we really? Language is as language does. Language is not a record-keeper (database), nor is it a model. But, if you insist ... my take is definitons may or may not be helpful in judging wether the term "modelling" is harmful or not, but I'm willing to come along.

> Leaving out the silly definitions
> like a person posing for a picture some useful definitions of model are:

(nothing silly about that, as I said earlier)

> 1. A miniature representation of a thing
> 2. Something intended to serve, as a pattern of something to be made
> 3. Anything which serves, or may serve, as an example for imitation
> 4. Any copy, or resemblance, more or less exact.

Nah. Suggested replacement: simplified repesentation to study some aspects. Think chemical model, simcity, prototypes, windtunnel, Bohr's atom, Marx's (&Ricardo's) capitalism, the nude on the sofa.

> 5. An abstract and often simplified conceptual representation
> of the workings of a system of objects in the real world

Hm... no purpose. Ok, forget 4 and provide 5 and 6 with a purpose.

> 6. a simplified description of a complex entity or process
>
> For "record", we leave out things like a 12" disc of vinyl, and we get some
> nice stuff. I like this first one out of Webster's for the verb record:
>
> To preserve the memory of, by committing to writing, to
> printing, to inscription, or the like; to make note of; to
> write or enter in a book or on parchment, for the purpose
> of preserving authentic evidence of; to register; to
> enroll; as, to record the proceedings of a court; to
> record historical events
>
> Here is the noun version:
>
> A writing by which some act or event, or a number of acts
> or events, is recorded; a register; as, a record of the
> acts of the Hebrew kings; a record of the variations of
> temperature during a certain time; a family record.
>
> Others:
>
> 1. That which serves to perpetuate a knowledge of acts or events;
> 2. anything (such as a document or a phonograph record or a
> photograph) providing permanent evidence of or
> information about past event

Nice going. Still with you, here. Suggested addition: 3. Form restricted registration of ... hm... of what? facts? That would leave out simulations, ok :
3. Form restricted registration of propositions.

> It should seem almost painfully obvious that the standard examples of
> employees, sales orders, inventory activity and so forth fit far more the
> definitions for "records" than they do for "model".

Both. Appearantly employees, sales orders, inventory activity and so forth are so common, that they serve as parts of the model we use to describe our day to day record-keeping problems in the abstract, i.e without having to resort to a specific business. Them being standard examples make them part of that aspect-model.

> One could stretch a
> point and contend that a sales order fits the definition of model because
> it is "Something intended to serve, as a pattern of something to be made",
> but really it is just instructions.

Generalized instructions, though. 'just instructions' would suggest _specific_ instructions, not usable for anything but the topic at hand. That's where (useful use of) the term 'model' comes in.

> Taking the other side, if you are using a database to do a huge weather
> simulation, then we argue that the application is modelling reality,

We? I would argue it models some aspects of reality, nothing more.

> but actually this is not so either.
> The tables cannot run the simulation, they
> can only record the results of some other program doing so. Though the
> records are the records of a model, they are still records, and are not
> themselves a model.

Ok.

> So where is the harm? Well, there is always a problem when you call a car a
> horse, because you risk stuffing hay down the gas pipe and you can really
> scratch the finish with those brushes. Any attempt to advance the theory
> of databases should understand them for what they are, or the theory will
> go off in the wrong direction.

'Calling a car a horse' is a mistake made often indeed. The nice thing about modelling is to make these acquired preconceptions (no this is not a contradictio in terminis, please think about it) explicit so we can see the differences between a car and a horse.

> Nor is the meta-data a model.

Indeed. It's just the record-keeping of the record-keeping mechanism - registering the forms.

> The meta-data for the employees table does
> not model the company, it specifies what information must be recorded to
> conform with law and policy. since meta-data is data, the meta-data is a
> record of what must be recorded. Still no model.
>
> Agree? Disagree?

I see benefits in using the term 'model' appropriately. Received on Wed May 04 2005 - 01:33:33 CEST