[tdwg-content] If you need something for referring to a population, then it is probably best to do it as a related class

[Hilmar Lapp]

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.

>   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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