Re: Objects and Relations

On 19 Feb, 01:01, "David BL" <davi..._at_iinet.net.au> wrote:
> 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:
>
> > > On Feb 17, 12:18 am, "JOG" <j..._at_cs.nott.ac.uk> wrote:
>
> > > > 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.
>
> > > 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.

Apologies if you thought it was tangential, but I feel your definition of an entity (or lack thereof) indicates the concepts lack of utility / as a whole/. This is an underlying problem I have with the whole 'entity' line of thought, and not just in the conversation with yourself.

However if you are saying an entity isn't a type, well that goes against the premise of Entity/Relationship modelling, which itself has such a big role in the current data management field. Again why are you using different definitions? It seems a lot of the communication problems here are because of you using different terminology to that which is accepted in the field. Either way, it is better to recognize this gap and bridge it, agreed?

> 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!

Well I can only quote you "Are you making a real attempt to understand me?". I mean you keep quoting "entities are illusionary" , even though we have clarified pages ago the intention of this statement. I think it adequately infers the mistake people often made in assuming that entities are anything but arbitrary concoctions.

But furthermore I have already offered that your confusion with the statement is just semantics, and you have ignored this. To clarify one more time, consider an analogy.

I am saying: "Unicorns don't exist."
You are saying "Unicorns do exist, look, I just imagined one" To which I reply "ok unicorns do exist, but they are something just made up in your mind".

Does that make more sense as to the semantic difference that you are (perhaps) obsessing over, but now seems to preventing further conversation?

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

What difficulties?

>
>
>
> > 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.
>
> > > 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.
>
> > > 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.
>
> > > 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.

No comment on this? I've offered to points indicating to how thinking in terms of entities can be unproductive - the lack of success of E/R modelling in replacing RM (which was its original goal), and the collapse of the entity-based manipulation of Classical AI in the 70's. There is insight in both of these. Received on Mon Feb 19 2007 - 14:42:35 CET