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Every property is a Class

From: Jonas Liljegren <jonas@rit.se>
Date: 20 Oct 2000 21:47:13 +0200
To: Graham Klyne <GK@dial.pipex.com>
Cc: Seth Russell <seth@robustai.net>, RDF interest group <www-rdf-interest@w3.org>
Message-ID: <87bswfwb0e.fsf_-_@jonas.rit.se>
Graham Klyne <GK@dial.pipex.com> writes:

>    [MyCar] --Model--> [FordEscort]
> 
> 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 feel that there is no difference between classes and properties.
Every property can be a class.


>    [MyCar] --Model--> [FordEscort]

[MyCar] --type--> [ModelFordEscort] --subClassOf--> [Model]


>    [TheBody] ----colour----> "Red"

[TheBody] --type--> [ColourRed] --subClassOf--> [Colour]


>    [TheEngine] --capacity--> "1600"

[TheEngine] --type--> [Capacity1600] --subClassOf--> [Capacity]


>    [TheEngine] --needs---->[repair]

[TheEngine] --type--> [NeedsRepair] --subClassOf--> [Needs]


Think about it.  Every property can be used to create the set of all
resoruces that have the property.  


If the engine needs repair, it's a member of the class of all things
that needs something.  We uses classes to provide a template for the
members.

We can use the words 'is' or 'has' in place of 'type'.  MyCar is
ModelFordEscort.  TheBody has ColourRed.  TheEngine has Capacity1600.
TheEngine NeedsRepair. (Need seems to be a basic type of type, on the
level of 'is' and 'has'.)

The 'is' often indicates that we want to create a class.  The 'has'
indicates that we don't think of the property as a class.  But that
distinction has more to do with language than logic.


TheBody has ColourRed.  This means that TheBody is a member of the set
of all things with the ColourRed. And that is a subset of all things
with a Colour.  Since Colour is a class, we can describe which
properties we expect the members to have. We can say that all things
with colour must have a degree of luminocity.  We can also say things
about the set; "There are two things that has the ColourRed".  And we
can say things about the proprty defining the set.




-- 
/ Jonas Liljegren

The Wraf project http://www.uxn.nu/wraf/
Sponsored by http://www.rit.se/
Received on Friday, 20 October 2000 15:42:29 GMT

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