Recursion Problems in Concatenation : A Case of Korean Morphology

Recursion Problems in Concatenation: A Case of Korean Morphology Kiyong Lee Department of Linguistics Korea University Seoul 136-701, Korea November 10, 1995 Abstract Without properly constraining recursions in generation, no language system can effectively operate. This is especially so with morphological generation, for each well-formed word must be finite in length and is ac- cepted as such only when it actually occurs in text or ordinary usage. This difficulty is compounded when a language system tries to maintain a single rule of concatenation and apply it repeatedly in order to combine a nominal or verbal stem with a sequence of suffixes in a time-linear man- ner. In an agglutinative language like Korean, however, it can easily be demonstrated how a language system like Malaga, based on time-linear grammars like Hausser's [1] Left-Associative Grammar, can properly be implemented to constrain undesirable recursive loops in generation. Both nominal and verbal concatenations in Korean are treated in this paper to show how infinite loops can be blocked by imposing appropriate matching conditions on two adjacent input strings to concatenation. 1 Introduction In Generative Grammar, the infinite magnitude of natural language is accounted for in terms of the notion of recursion. Without it, no syntactic embedding as in relative clause formation or that-complementation in English or even repeated modification as in an adjectival phrase "very, very, very long" can be explained with mathematical elegance. In an ideal agglutinating language there is no problem of morphological re- cursion because the number of suffix classes is finite and their order of occurrence is fixed: (1) Stem--SX1--Sx2--....-nn Furthermore, each position may be filled only once. 215 However, Korean deviates from the ideal type of an agglutinating language, because certain suffixes may occur in a reversed order: (2) Stem--...SX1.--sx...SXn (3) Stem--...sx--SX1...SXn A particular suffix sx generally appears after SX1, but it may also appear sometimes before SX1. The recursion problem resides in the possibility of re- adding sx after the string ...sx–SX1 because sx normally occurs after SX1. Using an implementation of Korean morphology in the Malaga system, this paper will present a straightforward solution to the indicated problem of re- cursion in Korean morphology. With one single rule for adding the particles or endings, recursively applied, both nominal and verbal forms are successfully generated, each consisting of a stem and a sequence of particles or endings. 2 Morphological Generation using Malaga Malaga is an acronym for "Malaga Accepts Left-Associative Grammar with Attributes" . As a language system' , it provides a general tool for both analyzing and generating word forms as well as sentences or text from left to right in a time-linear manner. In order to run the tool for a particular language like Korean, several specific files must be written. Among them are two list files, say korean.seg and korean.lex, and two rule files, korean.all and korean.mor.2 Consider the following nominal and verbal forms in the basic lexical entries of Korean: (4) korean.lex a. nominal forms [Phon: "pwumo",� [Phon: "kyoswu",�Class: N, Sem: "parent"]; Class: N, …

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