Abstract: Ontology is becoming one of the important research points in the area of semantic Web, which is enable to fulfill knowledge appearance, information retrieval. And as the basis of ontology description language, description logic is the formal tool of knowledge representation and reasoning, providing strong capabilities of representation and effective reasoning service mechanism, which has been extensively applied to various fields of compute science, such as artificial intelligence, database, information collaboration system and knowledge management. This paper detailedly studies the theory of description logic and its reasoning mechanism, proposes a new algorithm named Tableaux-RALU, and finally verifies the practical reasoning in the process of the concrete ontology construction.

Key words: description logic, reasoning mechanism, ontology construction