关键词: 本体, 子本体, 本体提取

Abstract: With wider and deeper application of the ontologies，ontologies tend to grow bigger and bigger.For specific users or agents，they may be interested in some subsets of an ontology.It is unnecessary for them to operator the huge ontology.So，there is high requirement that user can extract sub-ontologies from an ontology base.According to the shortages of previous research，this paper proposes a user sub-ontology extraction and simplification method that can protect hierarchical relationship，output sub-ontologies without any extra user interference，and reduce the workload of users.

Key words: ontology, sub-ontology, ontology extraction