Towards a New Computational Lexicon for Italian: building the morphological layer by harmonizing and merging existing resources
Authors: Flavia Sciolette, Simone Marchi, Emiliano Giovannetti (CNR-ILC, 2023)
Topic: Lexical and Semantic Resources and Analysis

Abstract
The present work illustrates the first steps towards the construction of a new computational lexicon for the Italian language. Following an analysis of existing lexical resources, it was decided to use LexicO as the reference base. In this first phase a resource of nearly 800,000 inflected forms was produced, accompanied by lemmas and morphological traits, obtained by integrating the available data in LexicO with those coming from two support sources: the tool MAGIC and a selection of Italian treebanks.

Introduction
A significant number of digital lexical resources are available for many languages. In CLARIN Virtual Language Observatory (VLO)1, a search for “lexicalResource” of Italian provides 52 results. Two resources appear in several versions and updates: Parole-Simple-Clips (PSC)2 [1], a multilayered lexicon, and ItalWordNet3. The most part of the results includes monolingual and multilingual domain terminologies. Amongst the notable resources are worth mentioning Italian Function Words (IFWs)4 and Italian Content Words (ICWs)5, two lists in JSON Lines format developed for supporting POS tagging and syntactic parsing of Italian. In fact, a number of NLP tasks can take advantage of lexical resources, for example sentiment analysis [2] but also “semantic role labeling, verb sense disambiguation and ontology mapping” [3]. However, ICWs includes hundreds of thousands of forms generated automatically and not manually revised, which, despite being morphologically correct, have very low, if not zero, usage frequency. Although not listed in Clarin’s VLO, we also mention SIMPLELex-it, since built similarly to our lexicon by combining various existing resources [4]. Even in lexical resources which have been manually developed and revised, however, the linguistic coverage of entries can pose problems, both in terms of lexical coverage and content of entries. Hence, integrating information from different sources, as we did in this work, can be effective in filling the gaps, though it can present several challenges in terms of harmonization of distinct formats and models. We here describe the first steps towards the construction of a new computational lexicon for the Italian language that we called CompL-it. We started from the enrichment of an existing resource, LexicO6 [5], a computational lexicon which, in turn, was derived from the already cited PSC lexicon. In particular, this first phase was focused on the expansion of the morphological layer, carried out through the integration of two other resources: a list of lemmatized forms generated by the morphological analyzer MAGIC7 [6, 7], and a set of Italian treebanks. The obtained resource, constituted of nearly 800 thousand forms, was made available in a CoNLL-like format as a tabular separated values (or TSV)8. This core of forms, lemmas, and morphological traits will populate the morphological layer of the computational lexicon CompL-it under construction, which will later be released in the form of Linguistic Linked Open Data (LLOD) (see Section 5). For this reason, it was chosen not to update the relational database of LexicO, but to use the CoNLL-like format as a temporary data representation format.

Conclusion
In this article, we documented a first step towards building a new computational lexicon of Italian. A set of approximately 800 thousand lemmatized forms with morphological features was created, through the integration of existing resources. In the next phases, this lexical core will be converted as a LLOD based on the OntoLex-lemon model, making the resulting lexicon more easily shareable, interoperable, and compliant with Semantic Web standards. Additionally, new linguistic layers will be added, starting from semantics, by using the information already available in LexicO and by integrating data from WordNets for Italian.