Construction of an Intelligent System for information Retrieval in an Environment of Information Network

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The project aimed at realizing an intelligent system for information retrieval over the Internet, The main results obtained are as follows.(1)Basic principlesUse of 'key concepts', estimation of relevance of retrieved results, and spoken dialogue as the user interface, were adopted as basic principles.(2)Processing of unknown wordsIn order to conduct search based on key concepts, the system has to infer the concepts of key words that are not registered in the system's lexicon. On the basis of an extensive collection and classification of such 'unknown words', methods were developed for processing unknown words arising from variations of transcription as well as unknown compound words consisting of known morphemes.(3)Processing of polysemy and synonymyIn order to realize concept-based search, both polysemy and synonymy of keywords have to be coped with. As for polysemy, a method for disambiguation was developed on the basis of collocation information. As for synonymy, a method was developed to expand a keyword on the basis of its concept.(4)Relevance estimation of retrieved resultsA method was developed for estimating the degree of relevance of a document to a query on the basis of number and location of occurrence of keywords within a document. The estimation was optimized to maximize the correlation between the estimated relevance score and the actual score based on human judgment.(5)Dialogue management based on user and system modelingA method for dialogue management was developed on the basis of analysis of simulated dialogues between a user and the system. It adopts separate modeling of the user and the system, represented by two finite-state automata exchanging information mainly through their utterances.(6)Construction of a prototype systemA prototype system was constructed combining the above-mentioned results, and its validity was tested and confirmed experimentally.