A finite-state morphological analyser for H ighland P uebla N ahuatl (2023)

Abstract: This paper describes the development of a free/open-source finite-state morphologicaltransducer for Highland Puebla Nahuatl, a Uto-Aztecan language spoken in and around the stateof Puebla in Mexico. The finite-state toolkit used for the work is the Helsinki Finite-StateToolkit (HFST); we use the lexc formalism for modelling the morphotactics and twol formal-ism for modelling morphophonological alternations. An evaluation is presented which showsthat the transducer has a reasonable coveragearound 90%on freely-available corpora of the language, and high precisionover 95%on a manually verified test set

## introduction this paper describes a new morphological analyser for highland puebla nahuatl, an endangered language spoken in the state of puebla in mexico (see figure 1 2 ). the analyser is based on finitestate technology, which means that it can be used for both the analysis and the generation of forms -a finite-state morphological transducer maps between surface forms and lexical forms (lemmas and morphosyntactic tags). an analyser of this sort has a wide variety of uses, including for automating the process of corpus annotation for linguistic research as well as for creating proofing tools (such as spellcheckers) and for lemmatising for electronic dictionary lookup for language learners -in a language with heavy prefixing and suffixing morphology, determining the stem is not a simple matter. our approach is based on the helsinki finite-state toolkit @xcite ). ## prior art finite state transducers (fst) for modeling morphology has a long history within the field of computational linguistics @xcite . work on morphological analysers for nahuatl languages includes an effort, inspired by literate programming, to use the code for the transducer as a descriptive grammar of a nahuatl variety spoken in the state of guerrero @xcite , and morphological analysers specifically targeting colonial-era nahuatl, either for the exploration of colonial texts @xcite , or as a means to evaluate similarity between written nahuatl varieties @xcite . one drawback of these projects is that they are not to our knowledge freelyavailable or easily-accessible. @xcite describe the development of morphological analysers and generators for more than one thousand languages using the johns hopkins university bible corpus @xcite , including some variants of nahuatl (however, not highland puebla nahuatl). @xcite presents the first open-source morphological analyser for the western sierra puebla nahuatl variant group. @xcite expand on that system, extending it to support huasteca nahuatl. this latter work, however, has not been released. ## highland puebla nahuatl nahuatl (or nahuat, nahual) is a polysynthetic, agglutinating uto-aztecan language continuum spoken throughout mexico and mesoamerica. the mexican government's instituto nacional de lenguas indígenas (inali) recognizes 30 distinct variants @xcite . highland puebla nahuatl, (or sierra puebla nahuatl, also referred to by inali as náhuatl del noreste central, iso-639-3 azz) is a nahuatl variant group spoken in the northeastern sierra region of the state of puebla, mexico, mainly in the municipalities of tetela de ocampo, zacapoaxtla, and cuetzalan. according to ethnologue's 2007 estimate, it is spoken by an estimated 70,000 speakers. this particular nahuatl variant has been the subject of a number of descriptive works @xcite @xcite and dictionaries (key and richie de @xcite . ## data the source data used to develop the fst comes from three sources: (1) a dataset of transcribed recordings of interviews and conversations, mainly about plants @xcite , (2) a subset of texts in the azz variant from the multi-variant parallel corpus axolotl @xcite , and (3) technical publications by the sociedad mexicana de física foot_0 , which consist of translations of various scientific texts. the breakdown of volume for each of these sources is presented in ## orthography writing practices in nahuatl vary and are characterized by multiple competing views (de la cruz cruz, 2014). the most well-known and widelydisseminated orthographic standards for nahuatl are ack, a colonial-inspired orthography named after scholars anderson, campbell, and karttunen, who popularized it in their work, the standard from the instituto nacional de lenguas indígenas (in-ali) @xcite , and that used by the secretaría de educación pública (sep). in practice, nahuatl writing contains a great deal of ortho-graphic variation, often even within the writing of a single author. the orthography used for building the analyser follows what was taught in the nahuatl course for adult learners given in the municipality of tetela de ocampo, puebla in the summer of 2022 (to). this broadly follows the sep, but with the addition of the letter h which is used before u for /w/ after vowels or at the beginning of words. for example sep ueueyi, to huehueyi 'big', sep mochiua, to mochihua "it is made". we maintain a separate finite-state transducer to account for orthographic and spelling variation. this includes rules for orthographic changes like ts (sep, inali) → tz (ack) (e.g. tejuatsin 'you-hon' → tehhuatzin), spelling changes, such as w@xmath0 and abbreviations that are found in the transcriptions from the spoken corpora, such as ^t' → ^tik. ## methodology in this section, we outline some of the implementation details of the analyzer, including a description of relevant linguistic features. ## results to evaluate the analyzer, we calculate the naïve coverage for both tokens and types. the naïve coverage is reported for each data source in ## concluding remarks we have described a robust finite-state morphological analyser for highland puebla nahuatl. this work contributes to the recent increased focus in language technologies for nahuatl, and may play an important role in supporting further nahuatl language technology in the future. in future work we would like to expand the lexicon to include more stems, to increase the coverage of all of the corpora, and to obtain new corpora for testing. we intend to include support for compounding and incorporation and for weighting the transducer. we already have 10,000 tokens manually disambiguated and will use these to weight more probable analyses.