UDante: First Steps Towards the Universal Dependencies Treebank of Dante's Latin Works
Authors: Flavio Massimiliano Cecchini, Rachele Sprugnoli, Giovanni Moretti, Marco Carlo Passarotti (Università Cattolica del Sacro Cuore, 2020)
Topic: Syntax and Dependency Treebanks

Abstract
This paper presents the early stages of the development of a new treebank containing all of Dante Alighieri’s Latin works. In particular, it describes the conversion of the original TEI-XML files to CoNLL-U, the creation of a gold standard, the process of training four annotators and the evaluation of the syntactic annotation in terms of inter-annotator agreement and LA, UAS and LAS . The aim is to release a new resource, in view of the celebrations for the 700th anniversary of Dante’s death, which can support the development of the Vocabolario Dantesco.

Introduction
The research field of treebanking (i.,e., the building of corpora enhanced with syntactic metadata) has evolved substantially since the time when the first large-scale syntactically annotated corpus, the Penn Treebank for English, was published between the late Eighties and the early Nineties AUTHOR. Across the last two decades, the range of languages for which a treebank is available has increased considerably. The grammar framework behind the most widespread annotation style currently used in treebanking has also changed: treebanks annotated according to various styles of dependency grammars have been increasingly outnumbering those based on constituency (or phrase-structure) grammars, as demonstrated by the current status of the Universal Dependencies initiative (ud) containing more than 160 treebanks and 90 languages which follow the same, dependency-based, annotation style AUTHOR. The set of textual genres covered by currently available treebanks is quite diverse. While the first corpora were built mostly collecting texts from news, the last decade has seen a substantial growth of treebanks of different genres, including literary texts, mostly written in ancient or historical languages. The first available treebanks for ancient languages were those for Ancient Greek and/or Latin, namely the Index Thomisticus Treebank (it-tb) AUTHOR and the Ancient Greek and Latin Dependency Treebank from the Perseus digital library AUTHOR. With regard to Latin, the available treebanks in ud cover just a minimal subset of the Latin texts that have survived the centuries and which show a wide diversity, mostly due to Latin's lingua franca role played all over Europe up until the 1800s AUTHOR. So far, the treebanks for Latin include only portions of the Classical and Late Latin canon of texts (Perseus and proiel AUTHOR), a set of Early Medieval charters from Tuscia (Late Latin Charter Treebank AUTHOR) and a selection of Late Medieval philosophical-theological texts by Thomas Aquinas (it-tb), for a total of more than 800,000 nodes. Among the many Latin texts that still lack syntactic annotation are those by Dante Alighieri (1265-1321). Given the importance of Dante in the history of Italian literature (and beyond) and in the light of the celebrations for the upcoming 700th anniversary of his death, we have started a project (called UDante) aimed at performing a ud-compliant syntactic annotation of all his Latin texts. The syntactic annotation of Dante's opera omnia in Latin fits into the larger project of the Vocabolario Dantesco, which aspires to provide a detailed description of the entire (both Vulgar and Latin) lexicon of Dante Alighieri. Indeed, during the composition of entries for the vocabulary, lexicographers will benefit from having the possibility to run syntactic queries on Dante's works. The choice of using the ud formalism in the UDante project is motivated by a number of benefits implied by the inclusion of a new set of annotated texts into such a large collection of treebanks sharing the same annotation style, among others the use of the several tools developed by the ud community with the goal of querying, editing, visualizing and (automatically) processing the (meta)data of the treebanks. Particularly, a remarkable added value is the possibility to run common queries on the almost 100 different languages provided with at least one treebank in the current version of ud (v2.6, released on May 15th, 2020). Furthermore, adopting a well known and widely used data format (CoNLL-U) and part-of-speech tagset (upos) fosters the dissemination and use of a treebank of Dante's Latin works in the community of computational linguistics, laying the foundation for a closer collaboration with that of Italian phylology and, more generally, with scholars in the Humanities, leading to a mutual benefit. This paper presents the process behind the development of the manually annotated ud treebank containing the full collection of Latin works of Dante Alighieri. More specifically, we describe the conversion of the original tei-xml files into the CoNLL-U format, we give details on the creation of a gold standard and we report on the training of four annotators with no previous knowledge of the ud formalism, providing an evaluation of their annotation work.

Conclusion
In this paper, we describe the preliminary steps towards the creation of a UD-compliant treebank of the Latin works by Dante Alighieri. To this end, we create a gold standard and we train and evaluate the work of a team of four annotators by means of a tripartite common set of sentences of increasing complexity annotated by a UD expert, complemented by specific gold standards for each annotator in a final control phase before the actual annotation work takes place. Besides supporting the objectives of the Vocabolario Dantesco project, the development of a treebank based on Dante’s Latin works also serves a wider scope, i. e. the inclusion of these latters into the LiLa Knowledge Base, which makes distributed linguistic resources for Latin interoperable through the Linked Data paradigm (Passarotti et al., 2020).16 At the same time, the efforts put into this project will hopefully bring forth some much-needed recommended guidelines for the UD-style annotation of Latin. The complete annotation of Dante’s Latin works will provide the community with a new, manually annotated dataset of higher quality than any automatic system. Table 4 reports LAS scores computed on the sentences of our gold standard and processed with UDPipe using the UD v2.5 models for Latin (Straka and Straková, 2017). The scores clearly show that current models are not good enough to parse the Latin of Dante. The addition of Dante’s Latin works into the thriving and expanding UD project and the newly acquired possibility to interact with a large number of other Latin texts of different genres and time periods makes us hope for a breakthrough of the world of treebanking into the wider community of the Humanities, which today can benefit from accessing a huge set of connected textual (meta)data like never before.