Coordinated Morphological and Syntactic Analysis of Japanese Language

A method for parallel morphological and syntactic analysis of Japanese language is proposed. Parallel syntactic analysis is based on an efficient parallel LR parsing algorithm for general context-free grammars. It handles syntactic features as constraints. Each syntactic feature is defined by a verbal sub-categorization and attached to a special set of phrases called bunsetsu in Japanese. The bunsetsu is used as a processing unit for both analyses. All processes act asynchronously, and are coordinated on a P-RAM(Parallel Random Access Machine). 1 Introduction In order to speed up natural language processing, efficient parallel processing methods must be developed. Recently, we have proposed an efficient parallel parsing algorithm for general context-free grammars which recognizes an input string of length n in O(n) time with O(n 2) processors and memory spaces [MiTaAm90b ]. This algorithm is optimal in the sense that, in general, almost 0(n 3) steps are required to recognize a context-free language on a sequential machine [Ear70, Val75 ]. Our algo-] rithm is based on an LR parsing scheme [Knu65 ]. This scheme offers two advantages: high speed analysis due to the compiled LR parsing table and the additional capacity of left-to-right on-line parsing[Tom87 ]. However, pure context-free grammars are not enough for natural language processing. It is often desirable for each symbol in the grammar rule to have attributes[Tom87 ] and for each grammar rule to allow an unrestricted word order. Particularly, in order to process a Japanese sentence, a parser must be able to handle an unrestricted word order. A morphological analysis, whose processes are themselves performed in parallel, must be performed in parallel with a syntactic analysis, and both analyses must be coordinated, so that the syntactic analysis may work up to capacity and they may perform together lexical dis-ambiguations using bits of information provided by the syntactic analysis. In this paper, a coordinated, parallel, morphological and syntactic analysis method is proposed. The parallel syntactic analysis performs a shift and a reducing action in parallel by using an LR transition diagram[MiTaAm90b ] which is derived from a pure context-free grammar and controls unrestricted word order by using syntactic features. The morphological analysis uses a finite state automaton called a morphological network. The morphological grammar and the syntactic grammar are integrated hierarchically. This integrated grammar is called a two-level grammar. By using this grammar, a terminal symbol of the syntactic grammar is used as a processing unit for both …