Sentiment analysis meets social media - Challenges and solutions of the field in view of the current information sharing context

In this introductory article, we briefly define the key concepts in Sentiment Analysis and describe present challenges faced by research in the task. Subsequently, we introduce each of the papers in this volume - chosen from an open call for papers and extended versions of the best papers presented at the 4th Workshop on Computational Approaches to Subjectivity, Sentiment and Social Media Analysis (WASSA 2013)- and we describe their contribution to the advancement of the current research in Sentiment Analysis. Finally, we conclude on the issues that have been tackled and those that remain open and reflect on the possible future developments of the field.