Re: DBpedia 3.2 release, including DBpedia Ontology and RDF links to Freebase

Hi Chris,

Chris Bizer wrote:
> Hi Hugh and Richard,
> 
> interesting discussion indeed. 
> 
> I think that the basic idea of the Semantic Web is that you reuse existing
> terms or at least provide mappings from your terms to existing ones.
> 
> As DBpedia is often used as an interlinking hub between different datasets
> on the Web, it should in my opinion clearly have a type b) ontology using
> Richard's classification.
> 
> But what does this mean for WEB ontology languages?
> 
> Looking at the current discussion, I feel reassured that if you want to do
> WEB stuff, you should not move beyond RDFS, even aim lower and only use a
> subset of RDFS (basically only rdf:type, rdfs:subClassOf and
> rdfs:subPropertyOf) plus owl:SameAs. Anything beyond this seems to impose
> too tight restrictions, seems to be too complicated even for people with
> fair Semantic Web knowledge, and seems to break immediately when people
> start to set links between different schemata/ontologies.

I do not fully agree. First of all, let's not forget that we also have
UMBEL and YAGO as two schemata on top of DBpedia data, which do not
impose many restrictions. People are free to use those (in particular
UMBEL is designed to by type b).

Regarding you arguments:

Too tight restrictions: Which ones specifically are too tight? If the
restrictions cause inconsistencies (which they are likely to do at the
moment), then this is a signal a problem in the DBpedia data. (Which is
one of the purposes of imposing restrictions.)

Too complicated: I don't have the impression that the people writing
here have no idea about the meaning of domain and range. Even if this is
the case, no one forces them to use them.

Breaks when you set links: True, so we should be careful in setting
those links to other schemata.

> Dublin Core and FOAF went down this road. And maybe DBpedia should do the
> same (meaning to remove most range and domain restrictions and only keep the
> class and property hierarchy).
> 
> Can anybody of the ontology folks tell me convincing use cases where the
> current range and domain restrictions are useful? 

I think there are many of those. First of all, they allow checking
consistency in the DBpedia data. Having consistent data allows to
provide nice user interfaces for DBpedia. Before this release, it was
hardly possible to write a user friendly UI for DBpedia data unless you
restrict yourself to a specific part of the data. One of the other main
problems was/is querying DBpedia. A better structure also helps a lot in
formulating SPARQL queries. We had questions like "How do I query the
properties of buildings?" etc. on the mailing list. Using the domain
restrictions, you can now easily say which properties you should query
and the range allows you to see what you will get (an integer value, a
string, an instance of a certain class etc.). This probably helps to
make more sophisticated use of Semantic Web structures, then we are
doing now.

> (Validation does not count as WEB ontology languages are not designed for
> validation and XML schema should be used instead if tight validation is
> required).

As a consequence, OWL should never be used for consistency checking?

> If not, I would opt for removing the restrictions.

What is the added value in removing the restrictions?

Kind regards,

Jens


-- 
Dipl. Inf. Jens Lehmann
Department of Computer Science, University of Leipzig
Homepage: http://www.jens-lehmann.org
GPG Key: http://jens-lehmann.org/jens_lehmann.asc

Received on Tuesday, 18 November 2008 07:33:38 UTC