The impact of phrases on Italian lexical simplification
Authors: Sara Tonelli, Alessio Palmero Aprosio, Marco Mazzon (Fondazione Bruno Kessler, Università di Trento, 2017)
Topic: Text Simplification

Abstract
Automated lexical simplification has been performed so far focusing only on the replacement of single tokens with single tokens, and this choice has affected both the development of systems and the creation of benchmarks. In this paper, we argue that lexical simplification in real settings should deal both with single and multi-token terms, and present a benchmark created for the task. Besides, we describe how a freely available system can be tuned to cover also the simplification of phrases, and perform an evaluation comparing different experimental settings.

Introduction
Lexical simplification is a well-studied topic within the NLP community, dealing with the automatic replacement of complex terms with simpler ones in a sentence, in order to improve its clarity and readability. Thanks to the development of benchmarks AUTHOR and freely available tools for lexical simplification AUTHOR, a number of works have focused on this challenge, see for example the systems participating in the simplification shared task at SemEval-2012 AUTHOR. However, the task has been designed as an exercise to replace complex single tokens with simpler single tokens, and most widely used benchmarks and systems all follow this paradigm. We believe, however, that this setting covers only a limited number of lexical simplifications as they would be performed in a real scenario. In particular, we advocate the need to shift the lexical simplification paradigm from single tokens to phrases, and to develop datasets and tools that deal also with these cases. This is mainly the contribution of this work, which covers four main points: \item We analyse existing corpora of simplified texts, not specifically developed for a shared task or for system evaluation, and we measure the impact of phrases in lexical simplifications \item We modify a state-of-the-art tool for lexical simplification in order to support phrases \item We compare different strategies for phrase extraction and evaluate them over a benchmark \item We perform all the above on Italian, for which there was no lexical simplification system available. Besides, we make freely available the first benchmark for the evaluation of Italian lexical simplification, with the goal to support research on this task and to foster the development of Italian simplification systems.

Conclusion
In this work, we presented a first analysis of the role of phrases in Italian lexical simplification. We also introduced the adaptation of Lexenstein, an existing lexical simplification system, so as to take phrases into account. In the future, we plan to test other approaches for the extraction of phrases, for example by applying algorithms for recognising multiword expressions. We also plan to integrate our best model for phrase simplification in ERNESTA AUTHOR, a system for syntactic simplification of Italian documents. Furthermore, within the H2020 SIMPATICO project, we will integrate our phrase simplification approach in the existing services of Trento Municipality and perform a pilot study with real users.