His main area of interest is web information retrieval, but in recent years he has focused on opinion mining and online social networks analysis. In 2013, he acted as guest co-editor for a special issue of Internet Research on the predictive power of social media. He has contributed a chapter on mining political opinion from Twitter to the forthcoming volume Twitter: A Digital Socioscope, edited by Yelena Mejova, Ingmar Weber and Michael Macy.