U niversal D ependencies for Suansu (2025)

Abstract: This contribution presents the Naga-Suansu Universal Dependencies (UD) treebank, the first resource of this kind for Suansu, an endangered and underdocumented Tibeto-Burman language spoken in Northeast India. This treebank follows the UD annotation framework. We describe the corpus composition, data sources, and annotation process, outlining the general structure of the treebank. In addition, we highlight morphosyntactic challenges where Suansu grammar does not fit neatly into the UD annotation schema and propose adaptations to better capture its structural properties. As the first Tibeto-Burman language included in the UD project, the Naga-Suansu treebank serves several purposes: it contributes to the documentation and preservation of endangered languages, enables the understanding of cross-linguistic variation, and supports future research efforts in refining UD annotation practices for South and Southeast Asian languages.

## introduction universal dependencies (ud) is a framework aiming to provide a unified grammatical annotation standard for a wide range of typologically diverse languages @xcite @xcite . thanks to its rich annotation capabilities and unified approach, ud has become an increasingly popular resource for cross-lingual nlp research, particularly for syntactic parsing and multilingual language modeling tasks. in addition, large ud corpora have been used in descriptive linguistics to explore internal syntactic variation @xcite as well as in cross-linguistic and typologically oriented studies @xcite . although the number of languages and treebanks has increased in the last decade, several language families and regions, including low-resource and endangered languages, are still underrepresented in ud. this contribution introduces the universal dependencies (ud) treebank for suansu (treebank name: naga-suansu foot_0 ), an endangered and under-described language spoken along the indo-myanmar border. to our knowledge, this represents both the first treebank corpus for suansu and the first ud contribution for the tibeto-burman language subfamily. developed in close collaboration with the suansu-speaking community, this resource aims to facilitate the inclusion of additional genealogically and geographically related languages into ud, enhance the typological diversity of ud corpora, and promote greater visibility and representation for under-resourced languages in language technology research. the paper is organized as follows. first, we introduce suansu language, outline its most prominent linguistic features, and clarify the naming conventions used for the treebank (section 2). section 3 describes the corpus and data sources, while in section 4 we detail the data preprocessing steps, describing the orthographic conventions (4.1) and lemmatization process (4.2). in section 4.3 we present the part-of-speech tags used in the treebank, and section 4.4 outlines the features in the treebank, with a more detailed discussion on converbs (4.5) and alignment (4.6). in section 5 we illustrate the dependency relations, with examples from copula clauses (5.1) and verb compounds (5.2). we conclude (6) with a summary and some directions for future research. ## suansu suansu is a tibeto-burman language spoken by approximately 2,000 people living in a small cluster of villages located in ukhrul district, manipur state, india, near the indo-myanmar border. it is an agglutinative language with a strong preference for suffixation and a strict verb-final word order, traits that are typical of languages in this region @xcite . prominent morphological processes include verb compounding and serialization. suansu morphosyntactic alignment does not fit neatly into the common alignment patterns described in the typological literature, a trait it shares with other regional languages such as meithei @xcite , poumai naga (veikho, 2021), and mongsen ao @xcite . suansu argument marking is primarily influenced by semantic and pragmatic factors rather than syntactic ones. our annotation schema to account for these distributions, developed per the universal dependencies guidelines, is described in section 4.6. suansu is an endangered language, and its documentation is ongoing @xcite @xcite : cross-village communication, education, and media predominantly use tangkhul naga, the regional lingua franca. thus, suansu lacks a standardized orthography. this paper offers a first orthography for the language, developed jointly with suansu community members and detailed in section 4.1. the decision to name the ud treebank "naga suansu" was motivated primarily by logistical considerations. suansu currently lacks an iso code (glottocode: suan1234), a requirement for registering ud treebanks. consequently, the treebank was assigned the iso code [nmf], originally designated for tangkhul naga. to clearly differentiate suansu from tangkhul within this shared coding scheme, we chose a term that could unambiguously encompass both languages in the future. after consultations with members of the suansu-speaking community, the term "naga" was proposed, as it better reflects shared ethnic affiliation while foregrounding linguistic identity. this choice aligns with established naming conventions among nearby languages (e.g., mao naga, poumai naga). however, readers should note that "naga" is an ethnic term without inherent linguistic implications. in this paper, we use naga-suansu to indicate the ud treebank, and suansu when we refer to the language. ## data the naga-suansu treebank comprises four distinct data sources, each translated into suansu by native speakers and subsequently manually glossed and annotated. the corpus contains 584 sentences and 3123 words across the four sources. a summary description of the corpus is available in the second source is the valpal dataset @xcite , comprising 101 sentences designed to investigate valency patterns across languages. the last two sources of treebank include 131 sentences from the bivaltyp questionnaire @xcite and 20 sentences from the cairo ci-cling corpus foot_1 . all materials were translated directly from english into suansu by native speakers, followed by manual interlinear morphological glossing and annotation. the choice of these sources is motivated by practical considerations, such as the availability of analyzed and glossed materials. at present, the corpus is skewed toward written data. we plan to include conversational data and additional spoken materials in future releases. ## annotation the data was divided into small batches, each containing fewer than 100 sentences. the first batch was converted from interlinear glosses into a conll-u file with tokenized sentences without annotated features and dependencies. morphosyntactic annotation for this initial batch was carried out entirely manually. subsequent batches were processed using the udpipe 1 pipeline @xcite , trained on the manually annotated data from previous batches. the resulting automatic parses were then reviewed and corrected manually. throughout the process, any ambiguous or previously unencountered structures were discussed collaboratively by the authors and native speakers to establish a consensus on the appropriate annotation strategy. ## dependency relations the universal dependency v2 lists 37 syntactic relations. of these 37 dependency relation types, thirty are used in the naga-suansu treebank foot_2 . dependencies and related counts are reported in ## conclusion we have presented the first treebank for naga-suansu, the first resource of its kind for suansu, an endangered language, and the first known contribution to universal dependencies from a language within the tibeto-burman subfamily. alongside the treebank, we introduced our approach to orthographic standardisation and detailed the partof-speech tags, morphological features, and depen-dency relations used in annotation, most of which align closely with the ud guidelines. where necessary, we proposed extensions, such as the addition of @xmath0, and offered a proposal for representing morphosyntactic alignment specific to suansu. we also addressed dependency relations for copular clauses and compounding. our future goals include expanding the dataset, by completing the ud annotation of the movie bridge of spies, which currently covers the first 300 sentences. we also plan to include annotated conversational data, further broadening the range of linguistic contexts represented in the treebank. finally, we plan on incorporating code mixing and multilingual influences, such as borrowings from the regional lingua franca tangkhul naga. through this work, we hope to encourage the development of additional ud treebanks for other tibeto-burman languages and to support a growing body of resources for endangered languages within the ud ecosystem.