Search Engines for Semantic Web Knowledge

Web search engines such as Google have made people "smarter" by making knowledge readily available whenever we need to look up a fact, evaluate options or learn about a topic. The Semantic Web effort aims to make such knowledge accessible to computer programs by encoding it on the web in machine interpretable form using RDF and OWL. As the volume of RDF encoded knowledge on the Web grows, software agents will need their own search engines to help them find the relevant and trustworthy knowledge needed to carry our their tasks. We will discuss the general issues underlying the indexing and retrieval of RDF based information and describe Swoogle, a crawler based search engine whose index contains information on over 1.3M RDF documents. Swoogle also serves human knowledge engineers by providing a means for them to find ontologies, terms and data and to understand how and by whom they are being used.