Type coercing a resource's type?

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.

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"

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

Received on Saturday, 22 February 2003 16:06:24 UTC