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The proposal and development of semantic web make ontology, as a new knowledge organization and semantic description method, get attention in various fields. The building of ontology is a basic and important task in semantic web. The construction method and organizational structure of ontology will directly affect the application of ontology. Based on the analysis of hierarchical characters existing in domain knowledge representation and organization and also the process of ontology building, this paper puts forwards a hierarchical construction method of ontology and gives the hierarchical construction principles in different ontology levels, which pays much attention to the hierarchical relationships in every stage of ontology building. And then based on this hierarchical construction method, this paper designs and builds a three-level geographical ontology applied in spatial information service. And also, this paper presents a description mechanism of ontology class metainformation to extend the description capability of OWL, which can help to well represent the difference and relationship between concept and term. The hierarchical identification in class meta-information can help to realize quick retrieving and matching of concepts based on hierarchical relationship.In the existing methods of ontology building, hierarchy mainly has two aspects of meaning: the overall structure of ontology is organized in the concept of hierarchy, and the building process of ontology adopts top-down or bottom-up hierarchical building method. [1][2][3] A. The overall hierarchical structure of ontology Ontology, according to the level of detail and the level of dependence on a particular task or point of view, could be classified into top-level ontology (concept-level ontology), domain ontology, task ontology and application ontology [4].Ontology in different levels could be used to realize knowledge representation and semantic analysis in different levels. At present, most of the existing domain ontologies are designed just for the purpose of certain application, which neglect the relevancies and constraints between different ontology levels. As a result, most of the existing domain ontologies lack the basis of top-level ontologies, which makes it not easy to map and integrate ontologies from different knowledge systems. The design of the existing ontologies does not fully adopt hierarchical structure as their overall structure. The boundaries of different level ontologies are blurry and interlaced together, which is disadvantaged for the maintenance and reuse of ontology. B. The hierarchical building process of ontologyThe top-down building method starts the design process from the overall view of domain knowledge and does not care about the details at bottom. This method is mostly used in the building of domain ontology with a certain scale and broader coverage, and it has very good expansibility and knowledge coverage. However, it is not easy to design top-level ontology, which requires the participation of domain experts and...

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