The Lemma Bank of the LiITA Knowledge Base of Interoperable Resources for Italian
Authors: Eleonora Litta, Marco Carlo Passarotti, Paolo Brasolin, Giovanni Moretti, Francesco Mambrini, Valerio Basile, Andrea Di Fabio, Cristina Bosco (Università Cattolica del Sacro Cuore, Università di Torino, 2024)
Topic: Lexical and Semantic Resources and Analysis

Abstract
The paper introduces the LiITA Knowledge Base of interoperable linguistic resources for Italian. After describing the principles of the Linked Data paradigm, on which LiITA is grounded, the paper presents the lemma-centred architecture of the Knowledge Base and details its core component, consisting of a large collection of Italian lemmas (called the Lemma Bank) used to interlink distributed lexical and textual resources.

Introduction
When considering the number of digital linguistic resources, either lexical or textual, Italian is among the richest languages: e.g., at the time of writing, a search on the CLARIN Virtual Language Observatory,} filtered for the Italian language, returns more than \num{8000} results. Like other high-resource languages, Italian is provided with a large set of fundamental resources, including WordNets ( AUTHOR and AUTHOR), a few treebanks available from the Universal Dependencies collection}, historical corpora }} and reference corpora of written (e.g., CORIS/CODIS AUTHOR) and spoken language (e.g., KIParla AUTHOR). However, as is the case for many other languages, most linguistic resources for Italian vary in terms of data format, annotation criteria, and/or adopted tagsets. Such variation hinders full interaction between the (meta)data provided by the many available resources, with a negative impact on the empirical study of the language and resource usability. Indeed, different resources may provide different information or use different granularity of information about the same common object, namely words, which appear as occurrences in corpora and as entries in dictionaries or lexicons. Making this wealth of information interact represents one of today's main challenges, to best leverage the huge asset of (meta)data collected over decades of work. As a consequence, a very active line of research currently focuses on the so-called Linguistic Linked Open Data (LLOD), aiming to define common practices for the representation and publication of linguistic resources according to the principles of the Linked Data paradigm, which underpins the Semantic Web), the ItalWordNet v.2 (), and a collection of names from the PAROLE SIMPLE CLIPS (PSC) lexicon ().}. A recently concluded COST Action (Nexus Linguarum}) resulted both in the creation of a large and cohesive scientific community and in the definition of a set of shared vocabularies for linguistic knowledge description. Some of these vocabularies have been widely applied in the LiLa Knowledge Base (KB), which is probably the main LLOD use case currently available. LiLa (Linking Latin) is a KB of Latin linguistic resources made interoperable through their representation and publication according to the Linked Data principles. Thanks to its streamlined and language-independent architecture, LiLa is today a reference model for projects aiming to achieve online interoperability between distributed linguistic resources. Building on the experience of LiLa and reusing its architecture, the LiITA (Linking Italian){http://www.liita.it/}} project has started the creation of a KB of interoperable linguistic resources for Italian published as Linked Data. This paper describes the development of the fundamental component of the LiITA KB, which consists of a collection of Italian lemmas (called the Lemma Bank) that serves as the connection point between word occurrences and their entries in the corpora and lexical resources that will be published in the KB.

Conclusion
In this paper we presented the first steps towards the publication as LLOD of a collection of canonical forms of citation (lemmas) for Italian. Such Lemma Bank is the core component of LiITA, a knowledge base of interoperable linguistic resources for Italian inspired by the LiLa knowledge base for Latin. LiITA aims to compensate the current lack of interoperability between Italian resources, as well as to become the pivot to interlink all the present and future lexicons and corpora for Italian. To this aim, the Lemma Bank is modelled such that it can harmonise different lemmatisation criteria found in lexical and textual resources, following a bottom-up approach rather that a top-down one. Building a Lemma Bank to make distributed resources interoperable in Linked Data is an open-ended process. As the linking of more and more resources to the KB might require the inclusion of new lemmas, the LiITA Lemma Bank will keep on growing, both through the extraction of lemmas from other lexical sources and in a resource-driven fashion. Beside extending the Lemma Bank and linking the first resources, the LiITA project will develop online services, following what has been done for LiLa AUTHOR. The process of linking a text or corpus in the KB must be supported by an accessible tool performing automatic lemmatisation, PoS-tagging and linking. Currently, a new Stanza model AUTHOR has been trained combining all the existing Italian treebanks. This model will serve as the foundation for the linkage process of textual resources to be included in the LiITA KB. in Appendix. The model can be found at \href{https://github.com/LiITA-LOD/LiITA_NLP_Models}{https://github.com/LiITA-LOD/LiITA_NLP_Models} The advanced interrogation of data offered by all the resources interlinked in LiITA will be eased by a graphical interface which will help with the task of writing complex SPARQL queries. Finally, given its language-independent architecture and the use of common vocabularies for knowledge description, LiITA promises to have a substantial methodological impact on how linguistic resources are published and made interoperable as Linked Data.