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Validation de réponses dans un système de questions réponses

Abstract : Question answering systems extract precise answers from a set of documents, and return the answers along with text snippets which justify them. For example, to the question "Who is the director of Avatar?" The answer "James Cameron" may be returned with "Avatar by James Cameron.".The answer validation detect automatically if the answer is valid ie. if it is correct (responds to the question) and justified by the text passage. This validation allows to improve the question answering systems by producing only valid answers.Two kind of methods can be used to detect right answers : -approaches using specific representation formalism of the question and the passage in which the structures are compared;-learning approaches that combines lexical and syntactic features.To identify the phenomena that characterize the answer validation, we built a manually annotated corpus. Differents phenomena can be seen like paraphrasing, coreference or that the information is spread in different sentences or documents. A second corpus aims to identify the different informations to be checked to valid an answer. This study showed that the three mains phenomena are the answer type, the date and place of the question.These studies have helped to develop our answer validation system which is based on a combination of features. The first one estimates the proportion of common terms in the snippet and the question, the second one measures the proximity of these terms and the answer. The second kind of features measure the compatibility between the answer and the question. Numerous questions wait for answers of an explicit type. For example, the question “Which president succeeded to Jacques Chirac?” requires an instance of president as answer.If the answer is not of this type then it is incorrect. The method aims at verifying that an answer given by a system corresponds to the given type. This verification is done by combining features provided by different methods. The first types of feature are statistical and compute the presence rate of both the answer and the type in documents, other features rely on named entity recognizers and the last criteria are based on the use of Wikipedia. Type checking is particularly effective because it makes 80 % correct detections. The final contribution was to integrate the validation module in a question answering system, QAVAL. Many answers are retrieved by QAVAL and ordered through the answers validation module. The module provide a confidence score to each response. QAVAL can be used both by researching the information in newspaper articles and in articles from the Web. The results are good, exceeding those obtained by a simple answer ranking from nearly 50%.
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Submitted on : Thursday, December 1, 2011 - 3:39:34 PM
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Arnaud Grappy. Validation de réponses dans un système de questions réponses. Autre [cs.OH]. Université Paris Sud - Paris XI, 2011. Français. ⟨NNT : 2011PA112241⟩. ⟨tel-00647152⟩



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