Semantic Web Talk Debrief

The Semantic Web talk at HJUG went fairly well. About eight people attended, and a few have either used RDF or are currently using RDF and OWL. The questions from the audience were insightful, demonstrating that they were thinking critically about the technologies. Some questions were quite expected:

Q) If anyone can say anything about anything, what's to stop someone from saying something wrong? How will I know *not* to use those incorrect assertions for my reasoning?

A) Good question! I have two solutions for this. The first is a Google-esque algorithm and hueristics will appear, allowing the top linked RDF documents to bubble to the top. That is, the more people that link to the RDF document, the more likely that the assertions contained within are valid for a majority of the views of the world. The second answer relies on ontologies, for they are able to determine if there are inconsistencies in the world. If someone says that cars and people are disjoint, and you have assertions in your RDF model that says X is a person and a car, then your reasoner can determine that at least one fact is incorrect. (of course, the hand waving here is that someone has to write the ontology, and you have to have a reasoner that provides feedback in a human readable way.)

Q) What if I use foaf:interest, but someone else uses yahoo:interest? My SPARQL queries won't work.

A) You're right, non-reasoning RDF stores won't know that foaf:interest and yahoo:interest are the same thing (for your view of the world). Again, ontologies are required to provide the mapping between different ontologies. *If* you have a mapping ontology, and *if* your RDF store performs reasoning, then your SPARQL queries will work when you have two URIs for the same concept.

Q) So... what have people built with RDF?

A) The answer I gave here is the biggest adoption of semweb technologies has been bioinformatics, afaik. However, I couldn't think of any business critical, production applications using RDF as a key component. I need to do more research here.

A better question might be, "What are some applications that utilize RDF/OWL that would have been very difficult to create otherwise?" And by applications, I mean business critical, production applications that customers use every day. I have a feeling that a lot of the RDF/OWL work is done for in-house, custom applications. What are those applications like? What scale have they been built out to?

All in all, a good talk. I met some people who are using Protege and Racer Pro to develop decision support applications for first responders. Don't know if it's a proof of concept of a deployed application yet.

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