Hi;

a little aside

On az., 2011.eko mairen 04a 04:34, Hilmar Lapp wrote:

On May 3, 2011, at 9:00 PM, Steve Baskauf wrote:

But I was under the impression that one models things by describing classes and the properties that connect them.

In OWL, properties connect instances, not classes. RDF allows metaclasses (things that are classes and instances), but doing this will throw most (all?) reasoners off the track.

Just to add to the discussion, puning can be used to model clases as instances. In fact, a common pattern I'm seing and I'm using is to use puning and have a class hierarchy, each class having an instance with the same URI, so one can refer to each class as a class or as an instance, depending on the context.

http://www.w3.org/2007/OWL/wiki/Punning

cheers

Classes are (to me) a very different thing than instances of classes. A model containing more than 13.6 million classes is at least 1.9 million times as complicated as a model with 7 classes.

Yes and no. I can model a taxonomy as a subclass hierarchy of classes, or as a property-based (memberOf or some such) hierarchy of individuals that all instantiate a single "Taxon" class. The former isn't 1 million times more complex than the latter. However, they are not identical either, and which approach one chooses has significant consequences for how easy it is to express things about those taxa, and for inferring new things from those with a DL reasoner.

I would hate to have to draw an RDF graph of that model

I would as much hate to have to draw an RDF graph of 1.7 million instances. The point being, in order to draw a graph of how someone models a domain you don't draw a graph of the entire RDF triple store.

-hilmar

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: Hilmar Lapp -:- Durham, NC -:- informatics.nescent.org :

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Mikel Egaña Aranguren, PhD
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Marie Curie post-doc at Ontology Engineering Group, UPM
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