Building a computational lexicon by using SQL
Authors: Alessandro Mazzei (Università di Torino, 2016)
Topic: Lexical and Semantic Resources and Analysis

Abstract
This paper presents some issues about a computational lexicon employed in a generation system for Italian AUTHOR. The paper has three goals: (i) to describe the SQL resources produced during the construction of the lexicon; (ii) to describe the algorithm for building the lexicon; (iii) to present an ongoing work for enhancing the lexicon by using the syntactic information extracted from a treebank.

Introduction
A number of free large multilingual resources covering Italian have been released, e.g. MultiWordnet, UniversalWordnet, BabelNet AUTHOR. Moreover, several lexical corpora have been built specifically for Italian, as the detailed map of the Italian NLP resources produced within the PARLI project shows}. Unfortunately most resources are designed to represent lexical semantics rather than morpho-syntactic relations among the words. As a consequence, these resources cannot be employed in statistical or rule-based natural language morho-syntactic analyzer or generator. A notable exception is the PAROLE-SIMPLE-CLIPS lexicon, that is a four-level (i.e. phonological, morphological, syntactical, semantic) general purpose lexicon composed by 53,044 lemmata AUTHOR. Unfortunately, a strong limitation for the usage of PAROLE-SIMPLE-CLIPS is the licence, since it is not freely available for research or commercial use. Rule-based natural language realization engines, that are systems performing linearisation and morphological inflections of a proto-syntactic input tree AUTHOR, need wide coverage morpho-syntactic information as knowledge-base. In other words, to perform realization, that is the last step of natural language generation AUTHOR, one needs two main kinds of linguistic knowledge: (i) the grammatical/syntactical knowledge that specifies the syntactic rules of the language and which is usually encoded into formal rules; (ii) the morphological and lexical knowledge, which is usually encoded into a computational lexicon. In the porting of the SimpleNLG system to Italian (henceforth SimpleNLG-IT) AUTHOR, we have used the grammar AUTHOR as the linguistic reference for the syntax: we have encoded the Italian syntactic inflections and word ordering by using IF-THEN-ELSE rules in Java. However, since Italian has a high number of irregularities for verb and adjective inflections, we needed for a specifically designed computational lexicon too. We needed for a lexicon that has both a good coverage and a detailed account of the morphological irregularities. In order to build this specific lexicon, that we have called SimpleLEX-IT, we have decided to merge three free resources for Italian, namely Morph-it! AUTHOR, the Vocabolario di base della lingua italiana AUTHOR and, for some specific issues, Wikipedia. The differences between the three resources can be referred to both the reasons for which the authors developed them and the adopted methodology and approach they applied in their development: the first is a hand-made list of basic words; the second one is an extensional corpus based morphological lexicon; the third one is a collection of encyclopedic entries about irregular verbs in Italian. This paper is organized as follows: in Section sql we describe the conversion of the three lexical resources used into a relational database; in Section lexicon we provide some details about the algorithm used to build SimpleLEX-IT; in Section wip we describe a work in progress to enrich the lexicon by using the syntactic information extracted from a treebank; finally, Section conclusions closes the paper with conclusions.

Conclusion
In this paper we have presented some issues about the computational lexicon SimpleLEX-IT. We described the algorithm used to build the lexicon, three SQL resources produced as side effects of the lexicon building and a work in progress about the extraction of syntactic information from UD-IT. %In future work we want to extend our treebank based approach for adjectives word order. All the resources described in this paper can be downloaded at .