Contrast-Ita Bank: A corpus for Italian Annotated with Discourse Contrast Relations
Authors: Anna Feltracco, Bernardo Magnini, Elisabetta Jezek (Fondazione Bruno Kessler, Università di Pavia, Università di Bergamo, 2017)
Topic: Lexical and Semantic Resources and Analysis

Abstract
We present Contrast-Ita Bank, a corpus annotated with discourse contrast relations in Italian. We annotate both explicit and implicit contrast relations, following the schema proposed in the Penn Discourse Treebank. We provide and discuss quantitative data about the new resource.

Introduction
A relevant task in Natural Language Processing is the automatic identification of semantic relations between portions of text, such as textual entailment, text similarity, and temporal relation. In this contribution we focus on discourse contrast. By discourse relation we mean a relation between two parts of a coherent sequence of sentences, propositions or speeches (i.e. discourse). We consider as discourse contrast: i) cases in which one of the two parts (henceforth arguments) is similar to the other in many aspects but different in one aspect for which they are compared, as in example (contrasto-conn-contrast), where both situations refer to a change in the price, but with different values; ii) cases in which one argument is denying an expectation that is triggered from the other argument, as in (contra-concession), where `going to the beach' denies the expectation that, since it is raining, one would stay home. Contrast in text can be conveyed explicitly, by mean of a lexical element (connective), as by while in (contrasto-conn-contrast) and although in (contra-concession), or implicitly as in (contrasto-conn-implicito). \ex The price of x increased of 5%, \underline{while} the price of y decreased of 2.3.% \ex \underline{Although} it was raining, we went to the beach. \ex Mary passed the exam. John failed it. We present Contrast-Ita Bank , a corpus of Italian documents annotated with contrast, a very frequent relation in discourse. We aim to understand how frequent the contrast relation is in discourse, when it is expressed explicitly and implicitly, and which are the connectives that convey contrast. The final result of the annotation represents a first step toward a corpus of discourse relations for Italian, compatible with the Penn Discourse Treebank (PDTB) project AUTHOR, the largest and the most used corpus annotated with discourse relations in the NLP field. A number of annotated corpora similar to the PDTB have been realised since its creation, for instance, the Prague Discourse TreeBank AUTHOR), the Chinese Discourse TreeBank AUTHOR), the Leeds Arabic Discourse TreeBank AUTHOR). propose an overview of projects also mentioning resources for French, Turkish and Hindi. For Italian, a similar attempt was proposed by AUTHOR, which uses the PDTB scheme for the annotation of the LUNA conversational spoken dialogue corpus. The authors annotated 60 real dialogues in the domain of software/hardware troubleshooting. Another project for Italian inspired by the PDTB is proposed by Pareti and Prodanof AUTHOR and it is focused on the relation of attribution, i.e ``the relation of “ownership” between abstract objects and individuals or agents'' AUTHOR. Resources manually annotated with discourse relation have been used for instance for developing methods and tools for the automatic identification and disambiguation of explicit marked or implicitly conveyed discourse relationsThe task of identifying discourse relations in the form of a discourse connective taking two arguments is also called shallow discourse parsing and constituted a shared task of the CONLL conference in 2015 and 2016 AUTHOR, for the identification of the spans of text that are linked by relations (discourse segmentation), for the automatic creation of a summary of a written text (text summarization) AUTHOR, and for machine translation AUTHOR. The paper is structured as follows: Section 2 introduces the contrast relation; Section 3 describes the annotation guidelines; Section 4 presents the content of the resource and Section 5 discusses the inter annotator agreement.

Conclusion
We presented Contrast-Ita Bank, a corpus annotated with discourse contrast relations in Italian. Following the PDTB annotation schema, we annotated explicit, implicit and altelex relations of contrast. We also present the list of connectives that convey contrast in the corpus. The new resource can be integrated with LICO, the Lexicon of Italian Connectives AUTHOR, validating the list of connectives and adding examples from corpus to the connectives. Contrast-Ita Bank is distributed under a CC-BY-NC 4.0 licence.