| Knowledge representation is an important branch of the artificial intelligence (AI). Knowledge representation started to be an independent research topic from the middle of 60's. For 40 years, people studied many methods of knowledge representation. The concept ontology origins from the philosophy domain. In the computer area domain ontology is a vocabulary with the specification of relationships between concepts in a special domain. Knowledge representation method based on ontology was one of research hot spots in recent years. This viewpoint thought that, any complex knowledge is made of the most basic concept, these most basic concepts is called ontology; Ontology is the specification of basic concept. The importance of ontology manifests its important role in knowledge reusing and sharing.Because the traditional intelligent teaching system resources lacks the uniform knowledge representation framework, all the learning resources are difficult to operate and share each other in various teaching system. At present the keyword-based knowledge information retrieval mode of ITS, being very limited in revealing semantics and pragmatics, is difficult to satisfy the users' actual demands. So it is very useful to research the knowledge representation of teaching system.The paper introduces ontology into the knowledge representation of teaching system, mainly researches on building of domain ontology, and by utilizing ontology achieves the semantic description and query of learning resource. The main contributions are summarized as follows:(1)Theory and method of knowledge representation and ontology have been described systematically on the basis of intensive investigation of large number of documents and web pages. The definition, type and role of ontology and knowledge representation have been described. The state of arts of ontology and knowledge representation research in China and foreign countries has been introduced.(2)Analyzing several commonly used methods for building ontology, to resolve the existing problems during the procedure of building, the paper designs an ontology building process based on seven-step method. Then we construct the ontology of Data Structure based on OWL representation, combing with the character of learning resource in content, structure, and application context, the paper describes the relationship between domain knowledge and learning resource, it achieves the mapping between domain ontology and learning resource, and probe into its validity according to building method. During the constructing of ontology, we adopt OWL (web ontology language) which is recommended by W3C as the ontology language. With the guidance of ontology building method, we use Protege 3.2.1 to write ontology file.(3)We try to develop a prototype system of semantic search based on Data Structure ontology. We study its principle development. Then by analyzing its Development tool, storage method, reasoning method, the process of semantic retrieval and the running results of the system, we think that the searching system based on semantic is more round and exact than the searching method based on keyword of traditional way.In order to provide the modeling of sharing concepts and semantic concepts, ontology is introduced to the knowledge representation of ITS. This not only solves the problem of knowledge sharing and operating and easily realizes the inquiry function based on semantic search, but also realizes semantic search based on conception easily. This can raised the precision and recall of information search system. |
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