W3C home > Mailing lists > Public > www-rdf-interest@w3.org > February 2003

Re: Type coercing a resource's type?

From: Yuzhong Qu <yzqu@seu.edu.cn>
Date: Sun, 23 Feb 2003 10:37:18 +0800
Message-ID: <002901c2dae4$7bfca9f0$9c0b77ca@xobjects>
To: "Roger L. Costello" <costello@mitre.org>
Cc: "RDF Interest" <www-rdf-interest@w3.org>

> Hi Folks,
> 
> Consider this class hierarchy:
> 
> 
>               BodyOfWater
>                |  |  |
>         --------  |  --------
>         |         |         |
>         |         |         |
>        Lake     Ocean      Sea
> 
> In my RDF Schema I have defined a property EmptiesInto to have a
> rdfs:range value of BodyOfWater:
> 
>     <rdf:Property rdf:ID="EmptiesInto">
>         <rdfs:range rdf:resource="#BodyOfWater"/>
>         <rdfs:domain rdf:resource="#River"/>
>     </rdf:Property>
> 
> Thus, when used in an RDF/XML instance the value for EmptiesInto can be
> a Lake, Ocean, or Sea.
> 
> Here's a sample RDF/XML instance which shows that the Yangtze River
> EmptiesInto the EastChinaSea:
> 
>     <?xml version="1.0"?>
>     <River rdf:ID="Yangtze"
>            xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
>            xmlns="http://www.geodesy.org/water/naturally-occurring#">
>        <Length>6300 kilometers</Length>
>        <EmptiesInto
>            rdf:resource="http://www.china.org/geography#EastChinaSea"/>
>     </River> 
> 
> From the RDF Schema I can infer that 
> 
>     http://www.china.org/geography#EastChinaSea
> 
> is a BodyOfWater.

Yes. But I think this style (using URIs without typing declaration) is harmful.
 
> However, I "should" be able to know more specifically that it is a Sea.
> 
> If this was a programming language I would do a type coercion to coerce
> it to Sea.
> 
> My question is this: is there something that I can do in the RDF Schema
> to indicate:
> 
>     "For the Yangtze River instance the property 
>      EmptiesInto has the more specific type Sea"

RDF Schema doesn't provide this kind of mechanism. OWL's property restriction (owl:allValuesFrom)  provides such functionality.

> That is, in an RDF Schema can I make statements about particular
> instances?  /Roger

Yes, but not about instances' property values.

Yuzhong Qu

> 
> 
Received on Saturday, 22 February 2003 21:34:03 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:51:58 GMT