Identifying Temporal Expression and its Syntactic Role Using FST and Lexical Data from Corpus

Accurate analysis of the temporal expression is crucial for Korean text processing applications such as information extraction and clmnking for efficient syntactic analysis. It is a complicated problem since temporal expressions often have the ambiguity of syntactic roles. This t)al)er discusses two problenm: (1) representing and identiflying the temporal expression (2) distinguishing the syntactic tim(lion of the temporal exI)ression in case it has a dual syntactic role. In this paper, temporal expressions and the context for disambiguation which is called local context are represented using lexical data extracted fiom corlms and the finite state transducer. By experiments, it; turns out that the method is eflimtive for temporal expression analysis. In particular, our al)t)roach shows the corI)us-based work could make a promising result for the t)roblem in a restricted domain in t, hat we can eflbctievely deal with a, large size of lexical data. 1 I n t r o d u c t i o n Accurate analysis of the temporal expression is crucial tbr text processing aplflications such as information extraction and for chunking for efficient syntactic analysis. In information extraction, a user might want to get a piece of information about an event. Typically, the event is related with (late or time,, which is represented by temporal expression. Chunking is helpflfl for efficient syntactic analysis by removing irrelevant intermediate constituents generated through parsing. It involves the task to divide sentences into non-overlatli)ing segments. As a result of chunking, parsing would be a problem of analysis inside chunks and between chunks (Yoon, et al., 1999). Chunking prevents the parser fl'om producing intermediate structures irrelevant to a final output, which makes the parser etticient without losing accuracy. Thus, it turns out that chunking is an essential stage tbr the application system like MT that should pursue both efficiency and precision. Korean, an agglutinative language, has welldeveloped flmctional words such as postposition and ending by which the grammatical fimction of a phrase is decisively determined. Besides, because it is a head final language and so the head always follows its complement, the chunking is relatively easy. However, we are also faced with an mnbiguity problem in chunking, which is often due to the temporal expression. This is because inany temporal nouns are used as the modifier of noun a n d vert) in a sentence. Let us consider the tbllowing examI)les: [Example] l a j inan(last) :l]('oFd'll,'llt(SlllillIler)