Re: [Welcoming feedback] Semantic Web: Information wants to be useful

On May 12, 2009, at 9:06 AM, David Baxter wrote:

> Pat Hayes said:
>
> > I know both Cyc and dbPedia say their
> > concepts are sameAs one another, but they are both wrong. Cyc  
> defines
> > a 'piece' of carbon; dbpedia defines the chemical element carbon.
> > These concepts are NOT owl:sameAs one another, no matter what the
> > websites say.
>
>
> Hi Pat,
>
> We're definitely interested in improving the quality of our  
> owl:sameAs links to DBpedia and other datasets. In this case,  
> however, I believe the owl:sameAs link is good -- it's the OpenCyc  
> comment that's bad. The URI opencyc:Carbon denotes an owl:Class  
> representing the element carbon. Its instances are individual pieces  
> of carbon, including diamonds and lumps of coal. We'll get the  
> comment fixed.

Hmm. So - just to see if I follow you here - Cyc thinks that a  
chemical element *is* the class of all its macroscopic pieces? Is this  
what DBpedia also thinks a chemical element is? Because (a) that seems  
to me to be a very idiosyncratic view of what a chemical element is,  
and (b) if DBpedia has some other ontology of chemical-element-hood,  
then your two concepts are very unlikely to the sameAs one another.  
Bear in mind that owl:sameAs really does mean logically identity, so  
ANYTHING said using one name is true using the other. So someone  
should be able to take any DBpedia content mentioning carbon, and any  
piece of Cyc content mentioning carbon, substitute one carbon name for  
the other throughout both chunks, and conjoin them, and the result  
ought to make sense in both systems. Is that indeed true, in this case?

Pat

PS. What does Cyc do about elements which only exist macroscopically  
as compounds? If there are no pieces of pure Ytterium, say, then the  
class Ytterium is the empty class. If there are no pure samples of  
Einsteinium, similarly. In an OWL reasoner, you could infer that they  
are the same class, hence sameAs one another (since they are both  
classes).

>
> David Baxter
> Cycorp

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