Re: "shape" as a relationship, not a class

On 2/9/2015 4:36, Karen Coyle wrote:
> I'm trying to understand how the subject of a triple can be either of 
> type shape or can have a shape.
>
> Let me make this more concrete. My subject is a book, which is a RWO, 

For a computer, your subject is not a RWO but a data structure 
represented by triples. Humans may interpret this as a real-world book, 
but this is IMHO largely philosophical.

> and it has an IRI. I'm going to make various statements about this RWO 
> (it has a title , it has an author, etc.). It makes little sense to me 
> to say that this RWO "has a shape/graph." The graph has a shape, but 
> using the same IRI to represent the RWO and the graph violates a basic 
> rule that each IRI references one and only one "thing."
>
> It seems to me that the key difference between shapes and classes is 
> exactly this: a shape is information about a graph; a class is 
> information about the RWO. If the class of the RWO  is coincident with 
> the graph that you wish to validate, then presumably the class can be 
> used as a target for validation. However, that is making a use of the 
> class which is not within the definition of class in RDF. I would find 
> it inconsistent with RDF for us to encourage people to assign classes 
> to RWO's that represent the graph itself.

Could you point me at documents that proof that all classes in RDF must 
be real-world objects? What about, for example, abstract data structures 
such as rdf:Lists - rdf:List is also a class. Also please consider that 
the term "class" is not exclusive to RDF Schema. It was already used by 
object-oriented systems, for example. I am afraid the distinction 
between real-world objects and their representation drifts into 
theoretical realms that nobody outside of the RDF world seems to care 
about (and rightfully so). I repeat my statement that there is zero 
practical difference between the following options:

     ex:Class
         a owl:Class ;
         rdfs:subClassOf [
             a owl:Restriction ;
             owl:onProperty ex:property ;
             owl:minCardinality 1 ;
         ] .

     ex:Class
         a owl:Class ;
         ldom:property [
             a ldom:PropertyConstraint ;
             ldom:predicate ex:property ;
             ldom:minCount 1 ;
         ] .

Holger

Received on Sunday, 8 February 2015 22:37:14 UTC