Effectiveness of Context-Aware Character Input Method for Mobile Phone Based on Artificial Neural Network

Opportunities and needs are increasing to input Japanese sentences on mobile phones since performance of mobile phones is improving. Applications like E-mail, Web search, and so on are widely used on mobile phones now. We need to input Japanese sentences using only 12 keys on mobile phones. We have proposed a method to input Japanese sentences on mobile phones quickly and easily. We call this method number-Kanji translation method. The number string inputted by a user is translated into Kanji-Kana mixed sentence in our proposed method. Number string to Kana string is a one-to-many mapping. Therefore, it is difficult to translate a number string into the correct sentence intended by the user. The proposed context-aware mapping method is able to disambiguate a number string by artificial neural network (ANN). The system is able to translate number segments into the intended words because the system becomes aware of the correspondence of number segments with Japanese words through learning by ANN. The system does not need a dictionary. We also show the effectiveness of our proposed method for practical use by the result of the evaluation experiment in Twitter data. 1. Introduction Ordinary Japanese sentences are expressed by two kinds of characters, that is, Kana and Kanji. Kana is Japanese phonogramic characters and has about fifty kinds. Kanji is ideographic Chinese characters and has about several thousand kinds. Therefore, we need to use some Kanji input methods in order to input Japanese sentences into computers. A typical method is the Kana-Kanji translation method of nonsegmented Japanese sentences. This method translates nonsegmented Kana sentences into Kanji-Kana mixed sentences. Since one Kana character is generally inputted by combination of a few alphabets, this method needs twenty six keys for the alphabets. Recently, performance of mobile computing devices is greatly improving. We consider that the devices are grouped into two by their quality. One gives importance to easy operation, the other gives importance to good mobility. Mobile phones are usable as mobile computers and belong to the latter group. Their mobility is very good because typical size of them is small. However, a general mobile phone has only 12 keys, which are 0 , 1 , … , 9 , ？ , and #, because of the limited size. A growing number of Smartphones, for example, iPhones, Blackberries, and so on, have full QWERTY keyboards. It is not easy to press the intended key because the key size is small. Moreover, a user needs to press a few keys per Kana character since one Kana