Scalable Query Answering over Linked Ontological Data
This event took place on Wednesday 15 July 2009 at 11:30
DR. Jeff Pan University of Aberdeen, UK
Scalable query answering over ontologies is one of the most useful and important services to support Semantic Web applications. For example, more and more ontological vocabulary used in linked data. Approximation has been identified as a potential way to reduce the complexity of query answering over OWL DL ontologies. Existing approaches are mainly based on syntactic approximation of ontological axioms and queries. In this talk, I will firstly give an overview of description logics in general, which are the underpinning of the OWL DL standard, and query answering over DL-based ontologies in particular. Then I propose to recast the idea of knowledge compilation into semantically approximating OWL DL ontologies with DL-Lite ontologies, against which query answering has only LogSpace data complexity. We identify a useful category of queries for which our approach guarantees also completeness. If time allows, I will also report on the implementation of our approach in the TrOWL system and preliminary, but encouraging, benchmark results which compare TrOWL's response times on queries in a well known ontology benchmark with those of existing ontology reasoning systems. I will conclude the talk with discussions on some future steps.
This event took place on Wednesday 15 July 2009 at 11:30
Scalable query answering over ontologies is one of the most useful and important services to support Semantic Web applications. For example, more and more ontological vocabulary used in linked data. Approximation has been identified as a potential way to reduce the complexity of query answering over OWL DL ontologies. Existing approaches are mainly based on syntactic approximation of ontological axioms and queries. In this talk, I will firstly give an overview of description logics in general, which are the underpinning of the OWL DL standard, and query answering over DL-based ontologies in particular. Then I propose to recast the idea of knowledge compilation into semantically approximating OWL DL ontologies with DL-Lite ontologies, against which query answering has only LogSpace data complexity. We identify a useful category of queries for which our approach guarantees also completeness. If time allows, I will also report on the implementation of our approach in the TrOWL system and preliminary, but encouraging, benchmark results which compare TrOWL's response times on queries in a well known ontology benchmark with those of existing ontology reasoning systems. I will conclude the talk with discussions on some future steps.
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Our research in the Semantic Web area looks at the potentials of fusing together advances in a range of disciplines, and applying them in a systemic way to simplify the development of intelligent, knowledge-based web services and to facilitate human access and use of knowledge available on the web. For instance, we are exploring ways in which tnatural language interfaces can be used to facilitate access to data distributed over different repositories. We are also developing infrastructures to support rapid development and deployment of semantic web services, which can be used to create web applications on-the-fly. We are also investigating ways in which semantic technology can support learning on the web, through a combination of knowledge representation support, pedagogical theories and intelligent content aggregation mechanisms. Finally, we are also investigating the Semantic Web itself as a domain of analysis and performing large scale empirical studies to uncover data about the concrete epistemologies which can be found on the Semantic Web. This exciting new area of research gives us concrete insights on the different conceptualizations that are present on the Semantic Web by giving us the possibility to discover which are the most common viewpoints, which viewpoints are mutually inconsistent, to what extent different models agree or disagree, etc...
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