We have introduced a search engine that can extract opinion sentences relevant to an open-domain query from Japanese blog pages. The engine identifies opinions based not only on positive or negative measurements but also on neutral opinions, requests, advice, and thoughts. To retrieve a number of opinion sentences that a user could reasonably be expected to read, we attempted to extract only explicitly stated writer's opinions at the sentence-level and to exclude quoted or implicational

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... . In our search engine, opinion sentences are identified based on features such as opinion clue expressions, and then, the relevance to the query of each identified opinion sentence is checked. The experimental results for various topics, obtained by comparing the output of the proposed opinion search engine with that of human judgments as to whether the sentences were opinions, showed that the proposed engine has promise as a practical application.