Handling Japanese Homophone Errors in Revision Support System for Japanese Texts; REVISE

Handling Japanese Homophone Errors in Revision Support System for Japanese Texts; REVISE Masahiro Oku NTI' Information and Communication Systems Laboratories 1-2356 Take, Yokosuka-shi, Kanagawa, 238-03 Japan E-mail oku@nttnly.ntt.jp Abstract Japanese texts frequently suffer from the homophone errors caused by the KANA-KANJI conversion needed to input the text. It is critical, therefore, for Japanese revision support systems to detect and to correct homophone errors. This paper proposes a method for detecting and correcting Japanese homophone errors in compound nouns. This method can not only detect Japanese homophone errors in compound nouns, but also can find the correct candidates for the detected errors automatically. Finding the correct candidates is one superiority of this method over existing methods. The basic idea of this method is that a compound noun component places some restrictions on the semantic categories of the adjoining words. The method accurately determines that a homophone is misused in a compound noun if one or both of its neighbors is not a member of the semantic set defined by the homophone. Also, the method successfully indicates the correct candidates for the detected homophone errors. 1 Introduction We have been using morphological analysis to develop REVISE, a revision support system that corrects Japanese input errors (Ikehara, Yasuda, Shimazaki, and Takagi, 1987; Ohara, Takagi, Hayashi, and Takeishi, 1991). REVISE can detect and correct various types of errors, such as character deletion, character insertion and some grammatical errors, using knowledge bases that describe the characteristics of each error type (see figure 1). Homophone errors are one of the error types that can be detected and corrected in REVISE. Most Japanese texts are made with Japanese word processors. As Japanese texts consist of phonograms, KANA, and ideograms, KANJI, lapanese word processors always use KANA-KANJI conversion in which KANA sequences (i.e. readings) input through the key board are converted into KANA-KANJI sequences. Therefore, Japanese texts suffer from homophone errors caused by erroneous KANA-KANJI conversion. A homophone error occurs when a KANA sequence is converted into the wrong word which has the same KANA sequence (i.e. the same reading). Therefore, detecting and correcting homophone errors is an important topic. Japanese sentence wire errors Morphglogieal An~ysls [ Error Detection ~¢ ~~nowKnowl~~ [Error Correction [~'-'--~Lor Variofis Errors J [,Display[ User chooses correct candidate Figure 1: Processing flow of REVISE. Previous research into detecting homophone errors with revision supportsystems used two approaches; (a) using correct-wrong word pairs (Kuga, 1986), Co) using KWIC (Key Word In Context) lists (Fukushima, Ohtake, Ohyama, and Shutoh, 1986; Suzuki and Takeda, 1989). Previous research into correct homophone selection in KANA-KANJI conversion used the following two methods; (c) using collocation of words (Nakano, 1982; Tanaka, Mizutani, and Yoshida, 1984; Makino and Kizawa, 1981). (d) using case frame grammar (Oshima, Abe, Yuura, and Takeichi, 1986). Method (a) has a drawback in that only pre-defined wrong words in correct-wrong word pairs are detected. Method (b) only indicates which words are in the KWIC list. Therefore, method (b) cannot automatically detect if the word is misused. Method (c) demands …

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