An Interactive Japanese Parser for Machine Translation

fin this paper, we describe a working system for interactive Japanese syntactic an',dysis. A human user can intervene during parsing to hell) the system to produce a correct parse tree. Human interactions are limited to the very simple task of indicating the modifiee (governor) of a phrase, and thus a non-expert native speaker can use the syst:em. The user is free to give any information in ;my order, or even to provide no information. The :.;ystem is being used as the source language analyzer of a Japanese-to-English machine translation ::;ystem currently under development. 1 I n t r o d u c t i o n I)espite the long history of research and development, perfect or nearly perfect analysis of a fairly ',vide range of natural language sentences is still beyond the state of the art. The users of the existing batch-style machine translation systems are obliged to post-edit the machine-translated text even if it contains errors because of an analysis failure. We haw~ developed an interactive Japanese syntactic analysis system, JAWB (Japanese Analysis WorkBench), for a Japanese-to-English machine translation system. It can produce very reliable .,~yntactie structures with the help of a human user. User interactions are limited to the very simple task of specifying the modifiee (governor) of a phrase, and thus a non-expert native speaker can use the system. The number of user interactions is minimized by using constraint pTopagation (Waltz 1975) to eliminate inconsistent alternatives. One feature of our system not found in previous a t t empts (Kay 1973, ~Ielby 1980, Tomita 1986) is that the user is completely free to give the system any information in any order. He also has the aiternative of providing no information, in this case, the system runs full;," automatically, although the quality of output may be degraded. In the next sectiom we describe the system structure. Then in Section 3 we discuss the interactive dependency analysis, and show a sample session. Section 4 gives the results of evaluation of the system. 2 S y s t e m S t r u c t u r e The system structure of JAWB is shown in Figure 1. Japanese syntax analysis is divided into two parts: morphological analysis and dependency analysis. An input sentence is first segmented into a sequence of linguistic units called bu'nsets'u, which can be roughly translated in English as phr'ase,s. Each bunsetsu, hereafter called a phrase, consists