Online acquisition of Japanese unknown morphemes using morphological constraints

We propose a novel lexicon acquirer that works in concert with the morphological ana-lyzer and has the ability to run in online mode. Every time a sentence is analyzed, it detects unknown morphemes, enumerates candidates and selects the best candidates by comparing multiple examples kept in the storage. When a morpheme is unambiguously selected, the lexicon acquirer updates the dictionary of the analyzer, and it will be used in subsequent analysis. We use the constraints of Japanese morphology and effectively reduce the num-ber of examples required to acquire a mor-pheme. Experiments show that unknownmor-phemes were acquired with high accuracy and improved the quality of morphological analy-sis.