K- SNACS : Annotating K orean Adposition Semantics (2020)

Abstract: While many languages use adpositions to encode semantic relationships between content words in a sentence (e.g., agentivity or temporality), the details of how adpositions work vary widely across languages with respect to both form and meaning. In this paper, we empirically adapt the SNACS framework (Schneider et al., 2018) to Korean, a language that is typologically distant from English—the language SNACS was based on. We apply the SNACS framework to annotate the highly popular novellaThe Little Prince with semantic supersense labels over allKorean postpositions. Thus, we introduce the first broad-coverage corpus annotated with Korean postposition semantics and provide a detailed analysis of the corpus with an apples-to-apples comparison between Korean and English annotations

## introduction korean has a grammaticalized category of postpositions that includes highly polysemous morphemes that mediate semantic relationships between content words. on their own, they represent humble grammatical markers on nominals, but they play a whale of a role in piecing together the meaning of a sentence. much like english prepositions (or collectively adpositions), the semantic relations that they encode range from thematic relationships like agentivity and instrumentality to relative circumstantial information like time, location, or purpose. in this work we develop a korean adaptation of an existing annotation schema, snacs ( §2.3), which is specifically geared towards adpositional semantics. the expanded schema details 54 semantic and pragmatic categories called supersenses that resolve major ambiguities and generalize across adpositional types. although the snacs framework was built based on english preposition senses, the authors claim that the semantically coarse-grained and lexically-agnostic characteristics of the supersenses are wellsuited to their adoption for other languages @xcite . the schema has been so far applied successfully to mandarin chinese @xcite . we now apply it to korean in order to further test claims of cross-linguistic extensibility. notably, snacs has yet to be tested on a highly agglutinative language like korean, whose adpositions (josa, §2.1) are bound morphemes suffixed on nominals, rather than independent lexical items like in english and chinese. korean adpositions are also peculiar in that some participate in case marking; we annotate postpositional nominative and accusative markers within the purview of snacs. our contributions are three-fold: (1) we show that snacs can be applied to korean by adapting the snacs hierarchy and guidelines to cover language-specific phenomena ( §3); (2) we produce a broadcoverage corpus of korean snacs annotations and provide a corpus analysis of the korean data ( §4); and (3) we provide in-depth comparison between parallel korean and english snacs for purposes of our own study and for basis of comparison for future application of snacs ( §5). 1 our work represents the first application of snacs to an agglutinative language where adpositions are bound morphemes. additionally, it represents a first korean supersense corpus that was specifically produced for korean postpositions. ## applying snacs to korean we apply the snacs supersenses to explicit mentions of korean postpositions, and we find that the labels are generally applicable to korean postpositional semantics. in this section, we discuss a few of the language-specific challenges we faced in applying snacs to korean. nominative and accusative cases one of the earliest challenges in adapting snacs to korean postposition semantics was deciding how to consistently label the nominative (nom) and accusative (acc) case markings. nom and acc case markings are postpositions that attach to the subject and object of a sentence, respectively. because these are identified in english via word order, there was no existing annotation scheme to follow in snacs. we adopt the view that the predicate's syntactic assignment of case marking such as nom and acc (as well as ergatives and absolutives) generally aligns with agentivity of the participant with respect to the verb given a transitive event @xcite . thus, for the function labels, we link the nom and acc labels to proto-agent and proto-patient roles @xcite , respectively, in a transitive event: nom (이/-i) foot_2 receives causer or agent function label and acc (을/-ul) receives the function of either theme (i.e., general undergoer) or its subtype topic (see example 3). in an intransitive event, where the nom marks the patient argument, the function label of theme is assigned (4). for cases where the predicate assigns to nom and acc semantics that is different to that of their prototypical use, we represent the semantics assigned by the predicate as the scene role (e.g., originator of a communication event in 5 and locus of an action in 6), while the function is the role associated most directly with the case marking (e.g. theme for acc). our decisions are fully compatible with the treatment of english subjects and objects proposed in @xcite al. (2019 ) (though available english snacs corpora do not yet contain such annotations). (3) 빌이/agent bill-nom 사과를/theme apple-acc 먹었다 ate "bill ate an apple" (4) 해가/theme sun-nom 일찍 early 떴다 rose "the sun rose early" (5) 빌이/originator↝agent bill-nom 대답했다 answered "bill answered" (6) 빌이/agent bill-nom 공원을/locus↝theme park-acc 걸었다 walked "bill took a walk in the park" contextual postpositions. english snacs has strictly focused on the annotation of semantic relations, excluding discourse connectives like "according_to him" or "as_for me" from annotation. we extend this treatment to two korean discourse markers: vocative marker 야/-ya and politeness marker 요/-yo. the pragmatic category in korean, however, extends beyond these two markers. korean also includes a category of frequently used pragmatic postpositions, whose role in a sentence is to evoke a particular set of contextual information regarding the entities to which they attach, thereby altering overall reading of the sentence. to address such usages, we introduce a new supertype context as a fourth branch of snacs hierarchy and add to it two new supersenses, topical and focus. we assign topical to postposition 은/-un that marks the information topic (top) in a sentence providing a contrast to a contextually available referent (7). focus label is for postpositions that indicate the focus of a sentence (foc), contributing information such as contrastiveness, likelihood, or value judgements (8 and 9). 4 there are a total of 10 identified postpositions that fall within the focus category. in the example below, the three sentences have the same propositional value (i.e., "bill did a good job"), but the postpositions situate the entity they mark within varying context. quotative postpositions the korean postposition inventory includes half a dozen markers that identify direct and indirect quotes in a sentence. the scene role that they play ranges from topic (10), identity (11), to comparisonref depending on the role assigned by the head verb. we propose a new supersense label quote, a subcategory of theme, to cover these at the function level. the placement of the postposition under the theme label was in recognition that these are participant arguments of verbs of communication (e.g., saying, telling) and cogitation (e.g., thinking, considering). what sets this usages apart from topic is that by virtue of being marked by a quote postposition, the sentence specifies that the information was heard or evidenced by the speaker/writer. korean quotatives have also been widely studied as an evidential marker, which is not fully captured by its placement under the theme. this is a topic of continued investigation. functionally bleached postposition 에/-ey scholars have noted 에/-ey marks inanimate entities for spatial, temporal and goal type relations @xcite @xcite . the postposition, however, is a highly bleached one: its meaning is largely dependent on the sense assigned by the predicate. on its own, it simply serves to specify that the nominal is in a certain circumstantial relationship with the predicate. for this reason, we specify circumstance at the function level, and let the scene role to disambiguate the relationship between predicate and the nominal foot_5 . postposition stacking because of the agglutinative nature of korean grammar, postpositional markers can productively stack on top of each other as exemplified by (1). postposition stacking is governed by grammatical rules and exhibits varying levels of grammaticalization @xcite . for snacs, we consider only six stacked postpositions as a single unit: 에게서/-eykeyse, 한테서/hantheyse, 에게로/-eykeylo, 에다(가)/-eyta(ka), 에서부터/-eyseputhe, and 으로부터/-uloputhe. these six have acquired noncompositional meanings. otherwise, the stacked postpositions (as in example 1) are considered compositional and annotated as separate targets. identifying postposition targets. we obtain automatic tokenization and morphological analysis via the koma tagger @xcite , which uses the morphological tagset from the sejong treebank @xcite . postpositions are not treated as separate tokens. for each token the tagger analyzes internal morphological structure (e.g., the word token 영국의 is analyzed as 영국/nnp+의/jkg "england+gen"). target postpositions are identified by a subword morphological tag starting with j. in the case of stacking, a nominal can have more than one such postposition (e.g., 너/np + 에게/jkb + 는/jx), in which case they are considered separate annotation targets. guidelines. in order to establish language-specific guidelines for korean discussed in §3, we first selected the first three largest chapters in within the first chapters of the novella (1, 2, 4). the three chapters were double annotated by two linguists-an expert in korean linguistics and a native korean speaker, using the original snacs guidelines established english. standards for korean snacs ( §3) were reached via analysis of disagreements during weekly discussions. ## korean vs. english: an inter-annotation discussion we chose to annotate the little prince as it has been widely translated, and already annotated (partially) for snacs in english @xcite . in this section we compare chapters 1-7 of korean and english little prince annotations. 7 for example, the verbal ending 려고/-lyeko marks purpose in a sentential complement like 내가 먹으려고 샀다 "i bought it for eating", and the nominal suffix (distinct category from postpositions) 쯤/-ccum marks approximate time in 1시쯤 "about 1 o'clock". these are currently under investigation for potential future addition to snacs annotation. 8 by way of comparison, @xcite applied snacs to english possessives in online reviews. ## conclusion & future work in this work, we have presented the first annotated corpus of korean preposition supersenses and included a detailed comparison of a subset of the data with a parallel english corpus. we find that, overall, korean and english adpositions cover similar semantic ground, making english snacs adaptable to typologically distant language like korean. still, applying the scheme to korean required us to establish new supersenses for pragmatic usages not found in english adpositions, and to develop policies for case marking, among other innovations. a number of directions remain for future work. one is an inquiry into supersenses that do not appear or appear infrequently in the annotated corpora ( §4.3). we believe there may be certain language-specific phenomena at play (e.g., multi-word postpositions) meriting further investigation. the english-korean parallel study also indicates a further need for investigating nuanced semantics like causality and force dynamics within the snacs framework. finally, as we have noted earlier, the snacs framework has been recently applied to mandarin chinese @xcite . preliminary adaptation efforts are also underway for hindi @xcite and german (jakob prange and nathan schneider, personal communication). all three initiatives target the little prince. these efforts thus herald an auspicious opportunity for cross-linguistic comparison of adposition and case systems.