file - ChaSen - 奈良先端科学技術大学院大学

ComputerHumanComputerHumanSpecializedBroadFigure 2.1. Three Viewpoints to Environment of Question-Answering.keyword inputs in traditional information retrieval and input forms of searchcondition in database retrieval are possible forms of queries.The provider of answer to user’s question restricts task performed by questionansweringsystem. For instance, if humans always provide answers to a question,the system only supports the humans who provide answers.The information sources to extract answer conditions the types of questionand the range of application. If a question-answering system aims to answerquestions related to certain domains and topics, required information sources arejust that comprising contents related to the domains and topics. Contrarily, if domainsand topics of question are unrestricted, it is necessary to equip informationsource comprising more broad contents. For instance, the World Wide Web is atypical information source containing broad contents. Additionally, the degree ofdifficulty to find answers is different regarding types of information sources. Forinstance, Q&A document contains relatively refined articles and directly exploitsthe association betweens questions and corresponding answers. In case of webpages, such prosperous conditions are however not existed.The question-answering system in this thesis supposes conditions of the environmentas follows,• The question-answering system accepts questions such that a human describeson the assumption that other human reads and answers the question.• A human does not only provide the answer but a question-answering systemalso answers to the same question.8