Re: RDF graph representation

At 14:45 22/07/04 -0500, Dimitri Glazkov wrote:

>This may be a bit of sophistry, but since predicate may be used as
>subject (and object, I assume) in RDF, doesn't this make a
>node-arc-node representation of a triple invalid?
>
>For instance, how would you represent an OWL property restriction in
>such a graph mode? Wouldn't this mean that you'd have to point an arc
>into the middle of another arc?
>
>Or am I missing something here? (which is probably the case)
>
>Illuminate me please..

It's fine, as others have said.

I find it useful to consider that the label on an arc indicates a *type* of 
arc, rather than a specific arc.  Then each arc that carries this label is 
an *instance* of such an arc.

This is borne out by the RDF formal semantics, in which the URI of a 
property indicates a "relational extension" (IEXT) of which a specific arc 
can be seen as a single member.  This is, in some respects, similar to the 
treatment of RDF classes which have class extensions (ICEXT) that are 
defined in terms of the relational extension of property known as "rdf:type".

In short, a label on an RDF arc is treated differently than a label on an 
RDF node.

#g


------------
Graham Klyne
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Received on Friday, 23 July 2004 18:14:36 UTC