Revisiting and Amending C entral K urdish Data on U ni M orph 4.0 (2023)

Abstract: UniMorph–the Universal Morphology project is a collaborative initiative to create and maintain morphological data and organize numerous related tasks for various language processing communities. The morphological data is provided by linguists for over 160 languages in the latest version of UniMorph 4.0. This paper sheds light on the Central Kurdish data on UniMorph 4.0 by analyzing the existing data, its fallacies, and systematic morphological errors. It also presents an approach to creating more reliable morphological data by considering various specific phenomena in Central Kurdish that have not been addressed previously, such as Izafe and several enclitics.

## introduction computational morphology, the study of word for mation using computational methods, is one of the important tasks in natural language process ing (nlp) and computational linguistics. this field has been one of the prevailing and longstand ing tasks with many applications in syntactic pars ing, lemmatization and machine translation @xcite . there have been remarkable advances and paradigm shifts in approaches to analyze and generate morphology: starting from adhoc approaches in the earlier systems, then rule formalisms and finitestate models since the 1980s @xcite ) with the no table example of kimmo twolevel morpholog ical analyzer @xcite , followed by statistical and classical machine learning since the 1990s as in @xcite , and more recently, approaches relying on neural network models since 2000s. lastly, more robust techniques are proposed us ing monolingual data hallucination (anastasopou los and neubig, 2019), transfer learning @xcite and pretrained models @xcite . unlike the progress in approaches, the depen dence of systems on clean and reliable data, re gardless of the size, for accurate morphological analysis and generation has not changed much. in order to bring together various linguistic com munities to create datasets and incentivize fur ther studies in the field, the unimorph foot_0 @xcite project has been a leading initia tive in this vein. in unimorph 4.0, the latest version of the project, there are 168 languages from various language families for which mor phological data is provided according to the uni morph schema @xcite . addition ally, the acl special interest group on compu tational morphology and phonology (sigmor phon) foot_1 has played an important role to organize workshops and shared tasks using the unimorph data. some of the previous shared tasks focus on crosslinguality and context in morphology @xcite , unsupervised morphological paradigm clustering @xcite and morphological inflection generation, segmen tation, and interlinear glossing in this year's task. one of the languages that is of interest in this paper and is also included in unimorph is central kurdish, also known as sorani (ckb). central kur dish, as a variant of the indoeuropean language kurdish, has a fusional morphology with several distinctive features due to its splitergativity, er ratic patterns in morphotactics and, several endo clitics used in verbal forms. these characteristics seem to be known to the unimorph community, as described in @xcite . however, the current data available for central kurdish con tains systematic errors and lacks coverage in mor phological forms. the data is also provided in a script that is not used by kurdish speakers, thus of no utility to downstream tasks in reality. con sequently, these result in poor performance of sys bound morphemes: noun:êk, an, gel, ha, at, eke, ekan, e, ane, gele, î (obl), ê, îne, {î, e} (iz) verb:in, de, e, bi, we, ne, na, me adjective:tir, tirîn adverb:ane @xcite , ser, řa, řo, wer tems that rely on the data in real scenarios. ## central kurdish morphology kurdish is an indoeuropean language spoken by over 25 million speakers in the kurdish regions in turkey, iran, iraq and syria, and also by the kur dish diaspora around the world @xcite . central kurdish, also known as sorani is the kur dish variant that is mostly spoken by the kurds within the iranian and iraqi regions of kurdistan. central kurdish is a nullsubject language and has a subjectobjectverb (sov) order and can be dis tinguished from other indoiranian languages by its ergativeabsolutive alignment which appears in past tenses of transitive verbs @xcite . in this section, we provide a brief de scription of central kurdish morphology by focus ing on morphemes and morphological processes. ## central kurdish on unimorph 4.0 in this section, we analyze the existing morpholog ical data for central kurdish on unimorph 4.0 and describe some of the current fallacies. the unimorph project provides a dataset for central kurdish that contains 24,316 wordforms. 3 this dataset was initially created within the alex ina framework @xcite by @xcite and focuses on inflectional morphol ogy by providing a set of forms of the paradigms of 252 lemmas with noun or verb partofspeech tags. overall, 33 morphological features based on uni morph are used in the dataset, including lgspec1 and lgspec2 which are respectively used for izafe morpheme î and its allomorph e. the number of features combined together is 226 features for all the word forms. in other terms, 0.98% of the word forms are assigned a unique combination of features. analogous to the notion of 'leakage' in syntactic parsing @xcite that reveals the overlap of the train and test sets, such a repeti tive usage of the features can cause an erroneously high performance of analysis models. as such, we believe that the dataset has very limited coverage of word forms and lacks diversity. in the following, we categorize some of the major issues of the central kurdish data on uni morph. ## methodology given the fallacies of the central kurdish dataset on unimorph 4.0, we believe that a new dataset is required for a thorough morphological analysis of this language. although we correct the exist ing dataset on unimorph 4.0, we also extend it with new lemmata and more complete paradigms. this measure was taken to ensure the quality of the forms based on a corpus and more importantly, in both conventional scripts of kurdish, namely the persoarabicbased and the latinbased scripts. in this section, we discuss our approach to creating a new dataset for central kurdish. ## conclusion in this paper, we discuss some of the fallacies of the current data of central kurdish on unimorph 4.0. we argue that the dataset is not only lacking coverage but also misrepresents kurdish morphol ogy by incorrect morphemes, unconventional writ ing and inaccurate morphotactics. additionally, we propose a new dataset with a few additional la bels for some of the features of central kurdish, such as izafe and various clitics. our dataset is gen erated using finitestate transducers with the hu man in the loop and are transliterated in the latin based script of kurdish in addition to the perso arabicbased ones. the transliteration of the word forms facilitates comparative studies, particularly with northern kurdish which is mainly written in a latinbased script. for each wordform, we also look it up in a corpus and provide the context in addition to the morphological features. moreover, we create a baseline by training models in various setups and evaluating them on our dataset and the current central kurdish data on unimorph 4.0. fi nally, we suggest this dataset be added to the future version of unimorph. limitations one of the limitations of our dataset is the lower number of wordforms belonging to a closeclass partofspeech as we chiefly focus on nouns, verbs (transitive and intransitive) and ad jectives. on the other hand, we only include in flectional morphology without paradigms of word formation. furthermore, we only address the mor phology of the standard variety of central kurdish, i.e. that of sulaymaniyah. we plan to extend our work to include other varieties of central kurdish along with derivational morphology. given that central kurdish lacks a treebank, it will be com pelling to bridge central kurdish morphology and syntax as well. another limitation of the current work is due to the unimorph schema. using the lgspec tag is not recommended for features that are found across languages but for those that are limited to specific languages @xcite . given that some of the features of central kurdish, such as izafe and pronominal copula, are also found in other closelyrelated languages, we believe that the current schema should be extended to use specific tags for such features or a better schema, akin to @xcite 's hierarchical model, is needed for languages with rich morphology like kurdish.