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file - ChaSen - 奈良先端科学技術大学院大学

file - ChaSen - 奈良先端科学技術大学院大学

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Period end? , etc.On the other hand, many online question-answering services, such as automaticanswering services, call centers, helpdesk and Q&A sites, have already beenestablished on the Internet and telephone networks. Q&A sites edit various questionsand answers in FAQ style presentation. The queries are not restricted tocertain domains, and the answers are written by the general public. Contrary tothe queries in TREC and NTCIR, their queries comprise many multiple sentencequeries.There are two major differences between queries in TREC and in actual QAServices. The first difference is the length of the queries and the number of thesentences, and the second difference is the question type. A TREC query isbasically a single sentence query (SSQ). Whereas a query in a QA service is oftena multiple sentence query (MSQ). The questions of TREC require mainly factoidanswers, such as a Person, an Organization and Location, but QA services musthandle many non-factoid questions requiring descriptive answers that consist ofa sentence or more, such as a Definition, a How-to and an Opinion, in additionto factoid questions. Although QA services have been supported by non-factoidMSQ, answers are extracted by humans. Figure 1.1 shows division of questionansweringsegmented by query, question and answer types in a tabular form.The queries in TREC can be assigned in the lower part of this table for factiodquestions, and that in actual Q&A services includes divisions in the upper partof this table. In the upperhalf of this table, this thesis mainly deals with queriesconsisting of multiple sentences and non-factoid questions requiring answers by asentence or more. In this thesis, this type of answer is called descriptive answer.To advance technologies of open domain question-answering to one that can applymore expanded query types such as those appearing in actual QA services, we haveto develop open domain question-answering that can deal with multi-sentencequeries and that handle questions requiring descriptive answers.1.2 Focus of this researchIn this thesis, we focus on two essential components to realize open domain multisentencequestion-answering. The first focus is Question Segment Extraction and2

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