Parsing Korean Honorification Phenomena in a Typed Feature Structure Grammar

Honori c agreement is one of the main properties of languages like Korean or Japanese, playing an important role in appropriate communication. This makes the deep processing of honori c information crucial in various computational applications such as spoken language translation and generation. We argue that, contrary to the previous literature, an adequate analysis of Korean honori cation involves a system that has access not only to morpho-syntax but to semantics and pragmatics as well. Along these lines, we have developed a typed feature structure grammar of Korean (based on the framework of HPSG), and implemented it in the Linguistic Knowledge Builder (LKB). The results of parsing our experimental test suites show that our grammar provides us with enriched grammatical information that can lead to the development of a robust dialogue system for the language. 1 Basic Properties of Honori c Agreement 1.1 Subject Agreement Honori cation, one of the main features of spoken language in Korean, plays a key role in proper and successful verbal communication ([?,?,?]). The Korean honori c system basically requires that when the subject is in the honori c form (usually with the marker -nim), the predicate also be in ected with the honori c form -(u)si as in (1): (1) a. sensayng-nim-i wus-usi-ess-e. teacher-HON-NOM laugh-HON-PST-DECL `The teacher laughed.' b. #sensayng-nim-i wus-ess-e. 4 We thank three anonymous reviewers for their helpful comments and suggestions. This work was supported by the Korea Research Foundation Grant funded by the Korean Government (KRF-2005-042-A00056). 5 Abbreviations we use in the paper include ARG (argument), ACC (accusative), BAKGR (background), COMP (complementizer), CTXT (context), DECL (declarative), HON (honori c), IMPER (imperative), NOM (nominative), ORTH (orthography), PST (past), SYN (syntax), SEM (semantics), RELS (relations), and POS (part of speech). This type of agreement is often assumed to be purely pragmatic, mainly because certain contexts allow disagreeing cases between the subject and the verb: the utterance of (1b) can be felicitous when the speaker does not honor the referent of the subject (marked by #). The possibility of having such disagreement has often led to an assumption in the literature that the cooccurrence of -nim on the subject and -si on the verb is a matter of gradience and appropriateness rather than grammaticality (cf. [?,?,?]). However, one often neglected fact is that this agreement constraint must be observed when the subject is non-human as in (2) (cf. [?]): (2) a. cha-ka o-(*si)-ess-e. car-NOM come-(*HON)-PST-DECL `The car came.' b. kwukhoy-ka pepan-ul simuy-ha-(*si)-ess-e. congress bill review-(*HON)-PST-DECL `The congress reviewed the bill.' In both examples, the nonhuman subject does not allow the presence of the honori c marker -si in the verb. If we rely only on pragmatic information, we would have di culty understanding why, in contrast to the disagreement in (1b), disagreement like that in (2) are rarely found in real language usages. In addition, there exist agreement-sensitive syntactic phenomena such as auxiliary verb constructions. Consider examples with the negative auxiliary verb anh`not': (3) a. sensayng-nim-i nolay-lul pwulu-si-ci anh-(usi)-ess-e. teacher-HON-NOM song-ACC sing-HON-COMP not-(HON)-PST-DECL `The teacher did not sing a song.' b. sensayngnim-i ton-ul mo-(*si)-e twu-si-ess-e. teacher-NOM money-ACC save-HON-COMP held-(*HON)-PST-DECL `The teacher saved money (for rainy days).' c. sensayng-nim-i nolay-lul pwulu-si-na po-(*si)-e. teacher-HON-NOM song-ACC sing-HON-COMP seem-(*HON)-DECL `The teacher seems to sing a song. As noted here, even though the subject is honored in each case, the honori c marker on the main predicate in (3a) is optional with the auxiliary verb anh`not'; in (3b) the marker must appear only on the auxiliary verb twu`hold'; meanwhile in (3c) the marker cannot appear on the auxiliary po `seem'. Such clear contrasts, we can hardly attribute to pragmatic factors. 1.2 Addressee Agreement Matters become more complicated when we consider the agreement triggered by di erent types of verbal endings. Korean has at least two di erent endings depending on the honoring relationship between speaker and addressee (cf. [?]): (4) a. haksayng-i o-ass-e/o-ass-eyo. student-NOM come-PST-plain.DECL/come-PST-resp.DECL `The student came.' b. sensayng-nim-i o-si-ess-e/o-si-ess-eyo. teacher-HON-NOM come-HON-PST-plain.DECL `The teacher came.' As noted here the verbal endings -e and -eyo are di erent with respect to addressee agreement. The `respectful declarative (resp.DECL)' ending -eyo is used when the social status of the addressee is higher than that of the speaker. The data implies that not only the speaker but also the addressee plays a role in proper communication strategies with respect to the honori cation system. 2 Honori cation in a Typed Feature Structure Grammar A closer look at the honori c phenomena of the language in the previous section suggests that an adequate theory of honori cation aiming for integration into a proper communication system requires not just complex pragmatic information but also syntactic and semantic information. The basic framework of the grammar we adopt for modelling the language is the typed feature structure grammar of Head-Driven Phrase Structure Grammar. This framework, HPSG, seeks to model human languages as systems of constraints on typed feature structures. In particular, the grammar adopts the mechanism of a type hierarchy in which every linguistic sign is typed with appropriate constraints and hierarchically organized. This system then allows us to express cross-classifying generalizations about linguistic entities such as lexemes, stems, words, and phrases in the language (cf. [?,?,?]). 2.1 Lexicon and Subject Agreement Our grammar, named KPSG (Korean Phrase Structure Grammar), rst assumes that a nominal with -nim and a verbal with -si bear the head feature speci cation [HON +]. This is supported by the contrast in the following: (5) a. [[haksayng-i manna-n] sensayng-nim-i] o-si-ess-e. student-NOM meet-MOD teacher-HON-NOM come-HON-PST-DECL `The teacher that the student met came.' b. [[sensayng-nim-i manna-si-n] haksayng-i] o-(*si)-ess-e. teacher-HON-NOM come-HON-MOD student-NOM come-(*HON)-PST-DECL `The student that the teacher met yesterday came.' As seen here, it is the honori c information on the head noun sensayng-nim in (5a) that agrees with that of the verb. With this head feature information, the grammar builds the honori c nominal type (n-hon) from the basic lexeme (n-lxm) as represented in the following feature structures: 6 The information our grammar encodes for such lexeme entries is only the shaded part: all the other information is inherited from its supertypes de ned in the grammar. For a more comprehensive system of morphology built within such a system, see [?,?].