The Research And Implementation Of Ontology-based Text Information Retrieval Technology

At present, with the rapid development of information technology, there are more requirements of accessing different types of information and a large number of information retrieval systems were developed to provide users with interesting contents. The traditional tools of information retrieval can only offer imports based on key words, but most time only key words can't express the real demands of the users which make the retrieval systems can't return the accurate results. To improve the precision of the information retrieval system, the transfer from the retrieval technology based on key words to the new version based on knowledge should be accomplished. Information should be semantically organized and expressed to design intellectualized information retrieval system.Because of ontology's good concept of hierarchy and good support upon the logical reasoning, it becomes more and more widely used in different fields, such as knowledge engineering, system modeling and so on. The information retrieval methods combined with ontology can not only emphasize the advantages of knowledge-based retrieval but also deal with the relationships between the various concepts. This dissertation proposes an Ontology-based Text Information Retrieval Framework (OTIRF) by combining the ontology theory with the traditional search technology.Firstly, this dissertation summarizes the shortcomings of traditional information retrieval, analyzes the characteristics of semantic retrieval and the role that ontology played in, summarizes the home and abroad research on semantic field and demonstrates the feasibility of solving the above problems by using ontology.Secondly, this dissertation studies the ontology modeling language and hierarchical structure, related techniques in the information retrieval. Then this dissertation proposes the structure of the OTIRF, introduces two major systems of the framework: query processing and ontology reasoning.Thirdly, this dissertation explains the structure of OTIRF and studies the key techniques used by the main module of the framework. In the part of query processing, this dissertation proposes two methods of query expansion and the formula for ranking the results. In the part of ontology reasoning, this dissertation introduces the concept of description logic and the related reasoning algorithms, studys the application of ontology reasoning in the OTIRF based on the tableaux algorithm.Finally, this dissertation represents the design and implementation of a Well Logging Data Retrieval Systems (WLDRS) which is based on OTIRF.