Re: Property instantiation

Hans Teijgeler wrote:
> Frank,
> 
> I wrote the code for the diagram "schema-basis", and tested that against the
> W3C Validator:
> 
> <rdf:RDF
>     	xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
>     	xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
>     	xmlns:owl="http://www.w3.org/2002/07/owl#"
>     	xmlns="http://www.example.org/ex#"
>     	xml:base="http://www.example.org/ex">
> 
>     	<owl:ObjectProperty rdf:ID="hasAsPart"/>
> 
> 	<owl:Class rdf:ID="Foo">
>     		<rdfs:subClassOf rdf:resource="#UserDefinedClass"/>
>     		<rdfs:subClassOf>
>        		<owl:Restriction>
>           			<owl:onProperty rdf:resource="#hasAsPart"/>
>           			<owl:allValuesFrom rdf:resource="#Bar"/>
>        		</owl:Restriction>
>     		</rdfs:subClassOf>
> 	</owl:Class>
> 
> 	<owl:Class rdf:ID="Bar">
>     		<rdfs:subClassOf rdf:resource="#UserDefinedClass"/>
> 	</owl:Class>
> 
> 	<Foo rdf:ID="foo_1">
> 		<hasAsPart rdf:resource="#bar_1"/>
> 	</Foo>
> 
> 	<Bar rdf:ID="bar_1"/>
> 
> </rdf:RDF>
> 
> So it seems that the "schema-basis" diagram was correct. 

I wouldn't have said the diagram was "correct", because there are some 
things in it that are puzzling, that is if it's supposed to be an RDF 
graph.

First, you have an arc between nodes labeled Foo and hasAsPart that has 
neither a label nor an arrowhead.  Then there is an arc between nodes 
labeled hasAsPart and Bar that has an arrowhead but no label.  I assume 
both those arcs are meant to represent the allValuesFrom constraint, but 
that's an unfamiliar diagrammatic convention to me;  in any case, in RDF 
graphs, arcs have (property) labels and directions.

Second, at the individuals "level", you have an arc labeled type from 
the hasAsPart arc up to the hasAsPart (class) node.  This type arc 
doesn't exist in an RDF graph.

If you run the Validator again, have it generate the graph, and compare 
it with your diagram, and you'll see what I mean.

The lesson, I think, is that a picture is only worth a thousand words to 
someone who understands the diagrammatic conventions used in the 
picture, since otherwise some additional words in explanation are 
necessary :-)

Yet you spoke about
> subclassing ObjectProperty, and that was the reason for the
> "schema-basis-alternative" diagram. It puzzles me what you meant with that.

I only mentioned subclassing ObjectProperty when I asked whether that 
was what you were trying to do.

--Frank

> 
> Regards,
> Hans
>

Received on Wednesday, 19 April 2006 17:17:15 UTC