Syllable-Based Model for the Korean Morphology

SYLLABLE-IIASED MOI)EI. FOR TIIF, K()III~AN MORPIIOLOGY Seung-Shik Kang Dept. of Computer Science & Statistics IIansung University Seonl 136-792, Korea Abstract This paper describes a syllable-based computational model for the Korean morphology. In this model, morpholovical analysis is considered as a process of candidate Generation and candidate selection. In order to increase tile performance of the system, the number of candidates is highly reduced and tim system require.s small number of dictionary accesses. Idiosynchratic features of a syllable, formalized as a characteristic fnnetion, make it possible to reject implausible candklates before dictionary confirmation, instead of a letter, syllable is a basic processing unit for the practical implementation of the morphological analyzer. 1. Introduction There are two linguistic phenomena that are interested in Ihe processing of computational morphology. They are morphological transformation and morpheme identification. Two-level model and syllable--based formalism focussed on the problem of morl)hological h'ansformntion IBear88, Cahig0, Kosk83]. Morpheme identification is an importmlt issue in some languages where two or more morphemes ave combined to make a word, a compound word, or a sentence without any delimiters between morphemes [Abe86, Chen92, Paeh92]. The goal of morphological analysis is to find the base form of morphemes in a word. It consists of a generation of analysis candidates and the selection of ton'cot candidates. Analysis candidates are generated as a reverse process of word formation rules'. morpheme isolation and morphological transformation. Then, correct candidates are selected by the coherence restrictions among Yung Taek KiIn Dept. of Computer Engineerin,q Sc~ul National University Seoul 15l-742, Korea adjacent morphelnes and dictionary confirnmtion. The morphological mmlyzer tries to generate all the possible candidates only to accept the correct candidates. 2. The l)roblem Two.-level model is widely known to be n eomputationnlly efficient method for the practical system on the condition thai the munber of rules is smnll[Bart86, Kosk88]. Howew.w, when the size of the rulebase is large it causes an exponential probleln. In case of the Korean langttage, it is common that a stenl is succeeded by I,,rammatical n~orphemes. If we use the twe-level model for a practical sys/eln, a small set of phonological rules and a large set of rnorl)helne isolation rules are required because there are several thousand colnbinalion.~ of grammatical morphemes[Zhan90]. in order to solve the problem, we can try a 2--pass algorithm. All the l)OS,~ible morl)hemes are isolated, and then do a phonological processing. It is also l~ossil)le to do a phonological processing first and morphemes are isolated at the second Imss. [iowever, this Mad of solution causes m~olller Selious problem that o(;eut+s l'totll the conditional resh'ie{ions: (1) ,,:eme morphologieal transformation occurs not only at a stem but also at a functional inorpheme, (2) there are eooccurrenee restrictions between two morl)hemes, (3) morphological tl'ansfovlnat[oll OCCtll'S only for the El)e.cinl word grotlp. 3. Syllable-based writing system The writina system for most languaffes i,~; based on tile letter set called as alphabet. Instead of' a letter se, t, Chinese writing 221 system is based on the set of characters that consists of one or …

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