Re: Objects and Relations

From: JOG <>
Date: 9 Feb 2007 07:25:45 -0800
Message-ID: <>

On Feb 9, 11:58 am, "David BL" <> wrote:
> On Feb 9, 12:09 pm, Gene Wirchenko <> wrote:
> > "David BL" <> wrote:
> > [snip]
> > >All the above comes down to definition. Your usage of "model" is
> > >different to mine. I restrict it to the narrow sense of the
> > >representation of knowledge (in the form of attributes and
> > >relationships) about external entities. I define "simulation" to be
> > By that, a clay model of an automobile would not be a model. I
> > think you have an overly-restrictive definition.
> The subject of this thread is a comparison of OO and RM. Does it
> matter if it doesn't encompass clay models? How is it too restrictive
> for database systems, RM or cdt?
> > >about creating a working machine that happens to *mimic* reality with
> > >no intention of storing knowledge about external entities. Are you
> > >saying such a distinction doesn't exist? If so then we disagree. If
> > >it is merely over what the words "model" and "simulation" mean there
> > >is nothing interesting to discuss.
> > A simulation is a model.
> > A model is a restricted representation of something. The
> > simplifications depend on what the model is to be used for. If a
> > model for aerodynamic testing, the shape of a car would be modelled.
> > The sound system probably would not be in the model (though the aerial
> > might be).
> Yes according to your definition a simulation is a model.

Few things. First when you are trying to express something to people in a certain newsgroup it is always beneficial to use the terminology specific to that domain if one wants to be listened to. Out of his own goodwill, mAsterdam maintains an extremely good glossary for the newsgroup, and that really should be the first port of call.

Second, it is worth noting that it has been written that Codd regretted naming his theories the relational "Model", very much because of this sort of confusion. RM is about recording and manipulating propositions, and not really about "modelling" at all.

Third, I am still not clear at all what the aim of this thread is. It all seems a bit like a lot of handwaving in search of an actual point. A point that I am yet to hear succinctly put. Received on Fri Feb 09 2007 - 16:25:45 CET

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