Research On OWL Ontology Querying Using Database And Reasoner

The rapid growing information volume in World Wide Web makes it difficult to access and maintain the information required by users. Semantic Web, the next generation web, aims to provide easier information access and usability by exploiting machine understandable metadata. In recent years, ontology, which enables a shared, formal, explicit and common description of domain knowledge, has been recognized to play an important role in Semantic Web. With the increasing use of ontology in Semantic Web, it is critical to supply an efficient method to query the information in the ontology.As the extremely large number of instances of real ontologies makes it difficult for DL reasoners to deal with ABox reasoning, and databases lack the ability to perform the inference sanctioned by OWL entailments, this thesis studies how DL reasoning and relational database systems can be combined to support queries about OWL ontology and proposes a new method which combines description logic reasoners for the TBox inference with logic rules implemented by sql for the ABox inference.First, this paper discusses a number of database schemas that can be used to store OWL data and discuss the tradeoffs of each. Then, it detailedly describes how to design a new database schema to support OWL entailments, and also explains how to store the concepts, properties, individuals and assertions in the database. On the basis of the database schema, a description logic reasoner is used to precompute the subsumption hierarchy and the information is stored into database. Next, the thesis studies the rules entailed in the axioms and implements the inference in ontology loading time and querying time to balance the loading time and response time.Finally, the thesis focuses on deffrent kinds of ontology querying and gives the specific algorithms to query the ontology.