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Proceedings of the 2006 Conference on Empirical Methods in Natural Language Processing (EMNLP 2006) , pages 355–363. Fully Automatic Lexicon Expansion for Domain-oriented Sentiment Analysis. Hiroshi Kanayama Tetsuya Nasukawa Tokyo Research Laboratory, IBM Japan, Ltd. Abstract.
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Proceedings of the 2006 Conference on Empirical Methods in Natural Language Processing (EMNLP 2006), pages 355–363. Fully Automatic Lexicon Expansionfor Domain-oriented Sentiment Analysis Hiroshi Kanayama Tetsuya Nasukawa Tokyo Research Laboratory, IBM Japan, Ltd.
Abstract • an unsupervisedlexicon building method for the detectionof polar clauses • convey positiveor negative aspects in a specificdomain • lexical entries acquired are called polar atoms • use context coherency, the tendency for same polarities to appear successively in contexts • the overall density and precision (94% in this work) of coherency in the corpus • the statistical estimation picks up appropriate polar atoms among candidates, without any manual tuning of the threshold values
Introduction • Sentiment Analysis (SA) is a task to recognize writers’ feelings as expressed in positive or negative comments, by analyzing unreadably large numbers of documents • Japanese sentence • in the digital camera domainSubjective (SA通常針對主觀句)Kono kamera-ha subarashii-to omou.‘I think this camera is splendid. [+] splendid(camera)Objective (客觀句在特定domain也有用處)Kontorasuto-ga kukkiri-suru.‘The contrast is sharp.’Atarashii kishu-ha zuumu-mo tsuite-iru.‘The new model has a zoom lens, too.’
Methodology of Clause-level SA(syntactic; 先根據日文文法) • sentence delimitation • proposition detection • Polarity assignment このカメラは素晴らしいと思う。 I think this camera is splendid このカメラは美しくない このカメラは美しいとよい 103 domain independent patterns 22 conjunctive patterns
Polar Atoms • a minimum syntactic structure specifying polarity in a predicative expression • [+] kukkiri-suru • ‘to be sharp’ • [+] tsuku <- zuumu-ga • ‘to have <-zoom lens-NOM’ • 3,275個
Context Coherency • 分Inter和Intra • ‘I think this camera is splendid.’‘It’s light and has a zoom lens.’‘Though the LCD is small, I’m satisfied.’ 雖然…‘But, the price is a little high.’但是… • Inter若遇到這些字
context coherency • an assumption that polar clauses with the same polarity appear successively unless the context is changed with adversative expressions • collect candidate polar atoms with their tentative polarities as those adjacent to the polar clauses which have been identified by their domain-independent polar atoms in the initial lexicon • Intra-sentential and inter-sentential contexts to obtain more candidate polar atoms
coherent precision and coherent density • coherent precision • coherent density • n=0 同一句, 1 隔一句 • Baseline所有positive比例
Unsupervised Learning forAcquisition of Polar Atoms • We can assume • cd(d,L+a)約等於cd(d,L) • cp(d,L+a)約等於cp(d,L) when L is large • confidence interval using approximationwith the F-distribution
Evaluation • Evaluation by Polar Atoms • two annotators evaluated 200 randomly selected candidate polar atoms in the digital camera domain • agreed upon in 89% of the cases and the Kappa value was 0.83 • Type Precision, Token Precision, Relative Recall • # of detected polar clauses with the expanded lexicon to the number of detected polar clauses with the initial lexicon
Robustness for DifferentConditions • Diversity of Corpora • Size of the Initial Lexicon