Abstract
This paper proposes a method to resolve intrasentential references of Japanese zero pronouns suitable for application in widely used and practical machine translation systems. This method focuses on semantic and pragmatic constraints such as conjunctions, verbal semantic attributes and modal expressions to determine intrasentential antecedents of Japanese zero pronouns. This method is highly effective because the volume of knowledge that must be prepared beforehand is not so large and its precision of resolution is good. This method was realized in Japanese to English machine translation system, ALT-J/E. To evaluate the performance of our method, we conducted a windowed test for 139 zero pronouns with intrasentential antecedents in a sentence set for the evaluation of the performance of Japanese to English machine translation systems (3718 sentences). According to the evaluation, intrasentential antecedents could be resolved correctly for 98% of the zero pronouns examined using rules consistent for intersentential and extrasentential resolution. The accuracy was higher than the accuracy of the centering algorithm which is a conventional method to resolve zero pronouns. By the further examination of the evaluation, we found that this method can achieve high accuracy using relatively simple rules.
