Re: Objects and Relations

On Feb 18, 12:36 am, "JOG" <j..._at_cs.nott.ac.uk> wrote:
> On Feb 17, 3:05 pm, "David BL" <davi..._at_iinet.net.au> wrote:
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> > On Feb 17, 12:18 am, "JOG" <j..._at_cs.nott.ac.uk> wrote:
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> > > On Feb 16, 4:40 am, Joe Thurbon <use..._at_thurbon.com> wrote:
> > > > David BL wrote:
> > > I am happy to put up with the definition of an entity describing a set
> > > of attributes/value pairs. All I object to is the concept that these
> > > sets are anything but arbitrary collections.
>
> > > To some people a 'book' requires an attribute stating whether it is a
> > > hardback or a softback. In other contexts a book might just be
> > > composed of its title, its content, etc. (a book published online
> > > perhaps). Please don't dwell on this example, it is just off the top
> > > of my head to show that 'entities' are artifices and vary incredibly
> > > from person to person and context to context. So as far as data
> > > management is concerned, keep 'entities' out, and let humans resolve
> > > such concepts outside of the logical model.
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> > You seem to be focusing on entity as meaning an abstract type, whereas
> > I'm tending to think of an entity as a particular thing.
>
> Your definition is meaningless as has been pointed out by several
> people. entity = particular thing, just begs the question of what a
> 'thing' is. You seem to have a circular definition that a thing = a
> particular entity.

Are you making a real attempt to understand me? That's a trivial strawman. It clearly wasn't a definition. It was in reference to your book example. For the purposes of stating facts about books, an entity would be a particular book, not some type "book". Classification is not necessary. It is irrelevant to the discussion.

> > Why are you doing that?
>
> I am trying to help you to a better definition, from which the limits
> of thinking in terms of 'entities' becomes clearer.

I can't understand your point. From my perspective you appear to make the simple mistake of thinking that because it's difficult to classify things, things don't exist!

I ask again, what's you point about the difficulties of classification?

> If it helps given the E/R-style 'entity' terminology you are holding
> onto, you might consider that I view /everything/ as an "associative
> entity". But of course I would not call it that.
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> > It is well known that classification of entities is
> > adhoc. Fortunately In DB systems we tend to state facts about
> > particular things far more often than sets of things.
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> > If I were to place an actual book in front of you, you could think of
> > hundreds of objective propositions about it. Actually the number of
> > possible propositions you could state about the book would seem almost
> > unlimited.
>
> > If you were given a different book, again there would be countless
> > propositions you could state about it. Now the book may have some
> > fundamental differences. Therefore attributes relevant to the first
> > book may not make sense for the second book and vice versa. This
> > makes classification of books difficult. However we both agree that
> > the RM copes well with that because it can represent knowledge about a
> > single book across lots of different relations. RM has no need to
> > develop a class hierarchy in the manner of OO (or indeed E/R
> > diagrams).

> It is good we are agreed of the benefit there, and an important point
> not to forget in all of this.
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> > What is more fundamental - facts about a particular entity, or the
> > entity itself? Surely the facts are secondary - at least for physical
> > entities.
>
> Well of course I don't accept there is anything but facts and values,
> so your question is nonsensical to me.

I guess your statement that entities are illusionary is nonsensical to yourself as well then.

> Remember that there are practical evidence of this standpoint having
> merit. For instance Symbolic AI died in the 1970's - a very real,
> practical example of how tyring to manipulate these elusive 'entities'
> results in failure. Situated and Nouvelle AI was born from this and
> I'd encourage you to check this area out - "Elephants don't play
> chess" by Brooks, is a good starting point.
Received on Mon Feb 19 2007 - 02:01:40 CET