Italian and English Sentence Simplification: How Many Differences?
Authors: Martina Fieromonte, Dominique Brunato, Felice Dell'Orletta, Giulia Venturi (Università di Pisa, CNR-ILC, 2019)
Topic: Text Simplification

Abstract
The paper proposes a cross-linguistic analysis of two parallel monolingual corpora conceived for automatic text simplification in two languages, Italian and English. The aim is to find similarities and differences in the process of simplification in two typologically different languages. To carry out the comparison, 1,000 sentences were extracted from the two corpora and annotated with a scheme previously used to annotate simplification phenomena.

Introduction
In recent years, the availability of parallel monolingual corpora has boosted the adoption of data-driven techniques for the task of automatic text simplification (ATS). These corpora are in general aligned at sentence level and consist of complex sentences paired with their simple version. However, except for English which can rely on two large parallel corpora, i.e. the Parallel Wikipedia Corpus2 AUTHOR (ParWik) and the Newsela corpus3 AUTHOR, these corpora are scarce or rather small in other languages. To reduce time and effort required for the construction of parallel corpora, some works tried new approaches to automatically or semi-automatically collect such resources, e.g. AUTHOR, AUTHOR, AUTHOR, AUTHOR. Moreover to take advantage of empirical data, most of these resources were annotated with rules aimed at identifying the typologies of modifications an original sentence goes through during the process of simplification. The inspection can be considered useful for several reasons: it permits i) to detect and classify a set of necessary transformations in TS, ii) to assess if a given corpus complies with user requirements and simplification tasks and iii) to evaluate the impact of simplification operations on target populations. If the corpus investigation also encompasses a cross-linguistic comparison, it might also shed light on peculiarities and similarities underlying the process of simplification across languages. However, so far this last issue has been rather ignored with the exception of AUTHOR, who compared how macro-simplification operations derived from different annotation schemes are distributed in Italian, Basque and Spanish parallel corpora. This paper intends to explore this under-investigated perspective and proposes a cross-linguistic analysis of two parallel monolingual corpora, i.e. the Italian corpus PaCCSS-IT (Parallel Corpus of Complex– Simple Aligned Sentences for ITalian) AUTHOR and the English Parallel Wikipedia Corpus AUTHOR. Through this comparison, the paper tries to answer the following three questions: 1. To what extent can an annotation scheme conceived for the annotation of simplification in one language be used to annotate simplifications in other language? 2. Are there any differences or similarities in the distribution and nature of simplification operations in the two languages? 3. If we find differences, to what extent do they depend on language only, or on the type of corpora? To answer these questions, 1,000 paired sentences were extracted from the two corpora and annotated with the scheme described in AUTHOR. This allows us to carry out a quantitative and qualitative analysis focused on understanding the nature of the modifications occurring in the datasets.

Conclusion
The paper proposed a cross-linguistic comparison between two monolingual parallel corpora for ATS. The comparison tried to answer three main questions. As regards question 1, the annotation stage proved the possibility to use, except few modifications, a language-specific annotation scheme for another language. More than language-specific factors, an in-depth analysis of the annotated pairs of sentences highlighted that the observed differences are due to linguistic phenomena characterizing different textual genres. This is the case for example of modifications due to the insertion of glosses, which is driven by the encyclopedic nature of Wikipedia pages rather than to the specific language. Similarly, textual genre has an impact on the linguistic level involved in the lexical substitution. The higher occurrence of substitutions at phrase level, rather than at word-level, reflects the attempt of Wikipedia editors to make scientific contents clearer and simpler for a wide target population. Corpus-design differences, especially those occurring between manually and automatically derived corpora, may affect the distribution of the simplification operations also within the same genre. This is one of the possible directions that we want to explore in the near future.