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Re: Chainsaw?

From: Tom Van Eetvelde <tom.van_eetvelde@alcatel.be>
Date: Mon, 23 Oct 2000 11:26:11 +0200
Message-ID: <39F40433.92A49DE6@alcatel.be>
To: Graham Klyne <GK@dial.pipex.com>
CC: Seth Russell <seth@robustai.net>, RDF interest group <www-rdf-interest@w3.org>
Hello Graham,

Graham Klyne wrote:

> [...] I'm trying to pursue the idea of contexts as a tool for structuring complex descriptions.
> (If
> that is a bad idea, I'm hoping someone will say, and explain why.)

Bad idea! :-) I believe my proposal can model in a more natural way what you want to do.

> I want to treat [FordEscort] as a resource that has various properties that
> describe that model of car, and, by reference, to have those properties
> apply to my car.
> Maybe [FordEscort] should be an rdf:Class?  I'm not quite comfortable with
> the idea that the model may be a class (hence object of rdf:type) and also
> an "ordinary" resource in its own right with lots of properties relating to
> some physical entity.

I think this discussion is closely related to an OIL discussion some weeks ago. There, we tried to
model 'Carnivore' as a subclass of 'animal' with some special properties.

Modelling FordEscort as a class doesn't seem strange to me at all. Personally, I like to see a class
as a set of elements that all share common characteristics. I like to explicitly state those
characteristics.However, the current RDF Schema spec doesn't support fixed property values of a
class. That's why I proposed to extend the 'domain' property.

I one states that Ford Escort is the set of cars with properties (I concatenate your subjects and

* bodystyle = Hatchback
* engine_fueltype = Petrol

then, just by instantiating the class Ford Escort, you immedialely get all these standard
properties, applied to your instance! With the 'extended version' of domain, you would get:

<rdfs:Class ID="Car"/>

<rdfs:Property ID="bodyStyle">
<rdfs:domain rdf:resource="Car"/>

<rdfs:Property ID="engine_fueltype">
<rdfs:domain rdf:resource="Car"/>

<rdfs:Class ID="Ford_Escort">
<rdfs:subClassOf rdf:resource="Car"/>
<s:bodyStyle> Hatchback </s:bodyStyle>
<s:engine_fueltype> Petrol </s:engine_fueltype>

With this approach, you can still see ford Escort as a resource that you can describe with
additioanl properties if you want. So it is a class and also an "ordinary" resource. I think this
solutions suits your needs.

If you really want to make the distinction: in context a , statement x is true and in context b it
isn't, then I think you have to stick to bags of statements.



Received on Monday, 23 October 2000 05:28:17 UTC

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