The Semantic Web is a vision for extending the Web so that machines
can more intelligently integrate and process the wealth of information
that is available. Unlike HTML and ordinary XML, Semantic Web languages
such as SHOE,
DAML+OIL, and
OWL
(a W3C Recommendation),
allow semantics (i.e., meaning) to be explicitly associated
with the content. The semantics are formally specified in ontologies,
which can be shared via the Internet and extended for local needs.
The SWAT lab is at the forefront of Semantic Web research
by studying issues such as interoperability of distributed
ontologies, ontology evolution, and system architectures and tools
for the Semantic Web. See the group's homepage
for details.
This paper presents an approach to querying the Semantic Web that considers the document-oriented nature of Semantic Web data. It defines queries in which one can ask what is entailed by a given subset of the documents in the knowledge base as well as queries in which one asks for which documents entail specificanswers. It provides algorithms for solving theses problems and describes an experiment in which many of the queries can be answered in miliseconds.
This is the first paper to discuss our attempts to realize the vision of the Semantic Web as a Web-scale query-answering system. We loaded nearly 350,000 real-world semantic web documents that committed to 41,000 ontologies into our DLDB system and then used additional "mapping ontologies" to integrate them. This experiment yielded promising results in that query times ranged from a few milliseconds to 5 seconds.
This is the definitive reference on the Lehigh University Benchmark (LUBM) and on empirical evaluation of Semantic Web knowledge base systems in general. This journal article coalesces the results from the ISWC 2003 and ISWC 2004 papers. In addition, it includes a discussion of preliminary tests on Jena and SPARQL versions of the benchmark queries.
This paper extends our benchmarking work by proposing an approach to generate a statistical model of a small OWL dataset and using this model to generate synthetic data of arbitrary size that can be used as a proxy for benchmarking purposes. In effect, this allows one to conduct scalability experiments on OWL domains for which large data sets are not yet available.
This paper, which won the Best Paper Award at ISWC 2004, is the first comprehensive experiment to compare different Semantic Web reasoners. Using our Lehigh University Benchmark (LUBM), we analyze the performance of Sesame (both a memory-based and data-based versions), OWL Jess KB and DLDB on different sizes of OWL datasets.
This paper discusses the crucial problems that occur when distributed ontologies evolve over time. It provides a formal semantics for ontology perspective theory, which is our recommended solution to the problem.
This paper describes the architecture of our DLDB system in detail. This system loosely couples a description logic reasoner and a relational database management system in order to retrieve complete answers for many extensional conjunctive queries on knowledge bases using a sizable fragment of OWL. This technical report is an extended version of the ISWC 2003 Practical and Scaleable Semantic Systems workshop paper.
Heflin, J., Hendler, J., and Luke, S. SHOE: A Blueprint for the Semantic Web. In Fensel, D., Hendler, J., Lieberman, H., and Wahlster, W. (Eds.), Spinning the Semantic Web. MIT Press, Cambridge, MA, 2003.
This paper is a summary of the SHOE language and tools. SHOE was the first Semantic Web language, in the sense that it was the first language designed for describing distributed ontologies using an XML-based syntax. The paper introduces many of the key issues that set the Semantic Web apart from traditional knowledge representation and provides a road map for Semantic Web research.
Heflin, J. and Hendler, J. Dynamic Ontologies on the Web. In: Proceedings of the Seventeenth National Conference on Artificial Intelligence (AAAI-2000). AAAI/MIT Press, Menlo Park, CA, 2000. pp. 443-449.
This is the first paper to discuss versioning and evolution for distributed ontologies. A semantics for SHOE is provided via a mapping to first-order logic. Special attention is given to versioning and the tendency of distributed ontologies to diverge in terms of semantic interoperability.
Please do not send me e-mail asking me to evaluate your chances of
admission to the department. I typically do not respond to such requests.
If you are interested in joining my research group, then send me an
e-mail that specifically describes what you would like to do and what prior
qualifications you have. However, I recommend that you read some of my
publications and explore our
current research first. If I think your interests
match our research, then I will contact you for further information.
Semantic Web Resources:
Semantic Web Activity at W3C
The World Wide Web Consortium's collection of specifications, working groups, and resources related to the Semantic Web.
SemanticWeb.org
A Semantic Wiki for the Semantic Web community. Includes information on tools, ontologies, people, and events.
SemWebCentral
A web site for non-developers to learn about the Semantic Web and for developers to share Semantic Web tools.
