Joint Annotation of Morphology and Syntax in Dependency Treebanks (2024)

Abstract: In this paper, we compare different ways to annotate both syntactic and morphological relations in a dependency treebank and we propose new formats we call mSUD and mUD, compatible with the Universal Dependencies (UD) schema for syntactic treebanks. We emphasize mSUD rather than mUD, the former being based on distributional criteria for the choice of the head of any combination, which allow us to clearly encode the internal structure of a word, that is, the derivational path. We investigate different problems posed by a morph-based annotation, concerning tokenization, choice of the head of a morph combination, relations between morphs, additional features needed, such as the token type differentiating roots and derivational and inflectional affixes. We show how our annotation schema can be applied to different languages from polysynthetic languages such as Yupik to isolating languages such as Chinese.

## case study in order to test our proposed annotation guidelines, we decided to approach a particular language, chukchi. chukchi (iso-639-3: ckt) is a highly endangered and polysynthetic language spoken in the sparselypopulated chukotka autonomous okrug in the far north east of the russian federation. the total population of chukotka was 50,526 in 2010. according to the 2010 census it was spoken by 5,095 people, or around a third of the ethnic population. today most speakers are over the age of 50, and, even by the 1990s intergenerational transmission had been disrupted @xcite . the language exhibits polypersonal agreement, ergative-absolutive alignment, and a subject-object-verb basic word order in transitive clauses. the language is severely under-resourced and there has been very little computational work on this language. we are only aware of a description of a finite-state morphological analyser (andriyanets and @xcite . there have been a number of theoretical and descriptive linguistic works on noun incorporation in chukchi, including spencer (1995) who gives a general overview and polinsky (1990) who covers subject incorporation. we used the amguema corpus, available through the «chuklang» foot_4 site, which is a corpus of spoken chukchi in the amguema variant. the corpus consists of both audio recordings and transcriptions with glosses and translations in russian and english. there are a total of 65 texts, most of which are elicited when compared to the analyses of other agglutinative languages. it utilizes morphs, without morphological features, as its fundamental units, thereby contravening ud's tokenization and word segmentation guidelines, which state: "morphological features are encoded as properties of words and there is no attempt at segmenting words into morphemes." a recent proposal by @xcite advocates reassessing how japanese treebanks' morph combinations align with ud's tokenization standards. the proposal introduces two new levels of morph combination to accommodate the distinctive nature of japanese verbal inflection, which is more fusional, in contrast to its less synthetic case marking. these challenges highlight that the determination of word boundaries operates independently and is orthogonal to the process of dependency annotation. for some languages, previous studies have proposed to have a partial annotation of the morphological level. this is the case in chukchi and in turkish. for chukchi, a polysynthetic language, tyers and mishchenkova (2020) are specifically interested into the annotation of noun incorporation. when a noun is incorporated in a complex morphological compound in which it plays the role of an object of a verb of the same compound, making the object relation explicit is important to account for the semantics of the construction. hence, they propose an encoding (see figure 2 ) where both the full compound (token 2) and the extracted noun (token 2.1) are represented (but not the other parts of the compound). for this, they misuse enhanced dependencies to encode a two-layer annotation in a context that does not correspond to the intended use of enhanced dependencies. for the turkish language, çöltekin (2016) explains that in some examples, it is difficult to avoid annotation at a subword level. they give example (2), in which the second token, arabadakiler, stands for two entities carrying different inflections. following current ud word conventions, it is impossible to have a sensible annotation because the adj mavi refers only to the sub-word arabada whereas the subject of the verb uyu is the subword kiler. çöltekin proposes to have a partial annotation at the subword level: a word is split into smaller pieces (named inflectional groups in turkish literature) only if "(a) parts of the word may have potentially conflicting inflectional features" or "(b) parts of the word may participate in different syntactic relations." if none of these conditions are met, the annotation is kept at the word level.