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Re: LANG: Knowing where thing come from (was Re: Lang: owl:ontolgy )

From: Jeff Heflin <heflin@cse.lehigh.edu>
Date: Fri, 20 Sep 2002 10:51:13 -0400
Message-ID: <3D8B35E1.105E52F9@cse.lehigh.edu>
To: Jim Hendler <hendler@cs.umd.edu>
CC: www-webont-wg@w3.org

Jim Hendler wrote:
> 
> At 5:42 PM -0400 9/19/02, Jeff Heflin wrote:
> >Chris,
> >
> >Just to refresh everyone's memory, this discussion began because of the
> >proposals for handling imports that are based in XML/RDF syntactic
> >inclusion. My whole point is that in every approach I've seen so far,
> >this form of inclusion loses track of which statements come from which
> >ontologies. In these cases, I no longer have the URLs of the documents;
> >they were lost when one document was inserted into another. If all OWL
> >parsers must perform this kind of inclusion, then people like me lose
> >the ability to do the things I mentioned.
> >
> >Note, I was not arguing that we need to modify RDF or OWL in some
> >radical way so that the model inherently includes source information
> >(I'll save that battle for OWL 2.0 :-). I simply want to make sure we
> >have solutions that don't prevent people who need source information
> >from doing what they want.
> >
> >Jeff
> 
> Jeff - wouldn't rdfs:IsDefinedBy [1] work?  - JH

The problem with IsDefinedBy is that it doesn't even make sense in RDF.
On the Semantic Web, there is no single place to "define" a resource.
The "definition" could be any number of RDF statements distributed among
many web pages. If you care about trust and things like that, then you
need to be able to to say which of the "definitional" statements come
from which ontologies. Currently, the only way to do that in RDF is to
use reification, as Jonathan has pointed out.

However, we also have the option to do it outside of RDF as Dan Connolly
does (by simply keeping track of URLs in his applications). Believe it
or not, I'm actually okay with this approach for now (we'll have to fix
the mess when we get to the trust level, but let's let another WG worry
about that). I only brought the point up because I believe that
approaches which rely on textual inclusion of XML syntax will prevent me
from figuring out the source of a statement because once you do the
inclusion, you no longer have the URLs of the individual files. For
example, if we use the XInclude approach, then an XML parser will output
a single DOM that merges the DOMs of the importing and imported
ontology. In the process, we have lost information (the sources of the
various RDF statements) that would have been valuable to my application.

In short, as long as we don't do an RDF/XML syntactic inclusion method
(that is option d to Question 1 from [1]), I believe my need for
"knowing where things come from" can be satisfied. If we can drop that
option from the table, then I see no point in arguing this issue
further.

Jeff

[1] http://lists.w3.org/Archives/Public/www-webont-wg/2002Sep/0272.html


> [1] http://www.w3.org/TR/rdf-schema/#ch_isdefinedby
> --
> Professor James Hendler                           hendler@cs.umd.edu
> Director, Semantic Web and Agent Technologies     301-405-2696
> Maryland Information and Network Dynamics Lab.    301-405-6707 (Fax)
> Univ of Maryland, College Park, MD 20742          240-731-3822 (Cell)
> http://www.cs.umd.edu/users/hendler
Received on Friday, 20 September 2002 10:51:16 GMT

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