High quality videos of tutorials and talks from the Seventh International Semantic Web Conference are now available on the excellent VideoLectures.net site. It’s a great opportunity to benefit from the conference if you were not able to attend or, even if you were, to see presentations you were not able to attend.

Videolectures captured the slides for most of the presentations (which are available for downloading) and their site shows both the the speaker’s video and slides in synchronization. Videolectures used three camera crews in parallel so were able to capture almost all of the presentations. Here are some highlights from the ~90 videos to whet your appetite.

• Introduction to the Semantic Web: An all-day tutorial featuring ten top researchers covering all aspects of the Semantic Web.
• How to Publish Linked Data on the Web: A three-hour tutorial by five researchers explaining how LOD works and how you can exploit it.
• Freebase: An Open, Writable Database of the World’s Information: A keynote by MetaWeb CTO John Giannandrea on Freebase.
• Semantic Web Challenge & Billion Triple Challenge: The session on the Semantic Web Challenge finalists.
• Semantic Wikis: Fusing the two strands of the Semantic Web: Mark Greaves on Semantic Wikis.
• Requirements Critic: A Tool for Automatically Analyzing Software Requirements Documents: The winner of the best paper award for the In Use track.
• Laconic and Precise Justifications in OWL: Winner of the best paper award for the Research Track.
• An OWL 2 Far?: A panel that takes up the question of whether having standard languages based on formal methods with steadily increasing power is the right way to support the Semantic Web.

Tom Briggs defended his PhD dissertation last month on discovering domain and range constraints in OWL and the final copy is now available.

Thomas H. Briggs, Constraint Generation and Reasoning in OWL, 2008.

The majority of OWL ontologies in the emerging SemanticWeb are constructed from properties that lack domain and range constraints. Constraints in OWL are different from the familiar uses in programming languages and databases. They are actually type assertions that are made about the individualswhich are connected by the property. Because they are type assertions these assertions can add vital information to the individuals involved and give information on how the defining property may be used. Three different automated generation techniques are explored in this research: disjunction, least-common named subsumer, and vivification. Each algorithm is compared for the ability to generalize, and the performance impacts with respect to the reasoner. A large sample of ontologies from the Swoogle repository are used to compare real-world performance of these techniques. Using generated facts is a type of default reasoning. This may conflict with future assertions to the knowledge base. While general default reasoning is non-monotonic and undecidable a novel approach is introduced to support efficient contraction of the default knowledge. Constraint generation and default reasoning, together, enable a robust and efficient generation of domain and range constraints which will result in the inference of additional facts and improved performance for a number of Semantic Web applications.