Research On Ontology Reasoning And Querying Based On The Non-monotonic Reasoning Ability

The Description Logic is the logical foundation of the semantic web, it can only deal with the objective and complete knowledge, so it has the inability of processing the subjective and incomplete knowledge. The epistemic Description Logic ALCK can express the epistemic querying to deal with incomplete knowledge effectively through epistemic operator, and preserve the Description Logic's advantage of describing the terminology knowledge in the field. The thesis achieves next results:Firstly, this paper introduces the Description Logic ALCR_+, the epistemic description logic ALCK and the conjunctive query in the Description Logic. The syntax, semantics and the algorithm for the querying and reasoning are represented. This knowledge is the foundation of the research;Secondly, aiming to solve the problem that the original epistemic description logic has the limited expressivity of the describing domain knowledge, the transitive role is added, and the new epistemic description logic ALCKR_+ is proposed. The syntax, semantics and teableau algorithm of this language is represented. The decidability and soundness of the tableau algorithm is proved. The computation complexity is analysised.Then, aiming to deal with the problem that the epistemic query has the limited querying expressivity in the epistemic description logic ALCK, the conjunctive query is considered, and the epistemic conjunctive query language in the epistemic description logic ALCK is represented.. This paper represents the syntax, semantics and query answering algorithm of the query language. The decidability, soundness and completeness of the decision procedure are proved. The computation complexity is analysised.At the end of the thesis, the major theory and research achievements have been summarized. The future research proposals have been made. The theoretical impact the achievements impose on semantic web research and development is described.