His research interests include Database and Information Systems, Data Science, Data and Text Analytics, Data Infrastructures and Digital Repositories, Recommender Systems and Personalization, and Human-Computer Interaction, topics on which he has published over 170 articles in leading journals and conferences and also holds four patents. His work is often inspired by and applied to data management and analysis problems that arise in industrial environments or in the context of other scientific fields (Social Sciences and Humanities, Life Sciences, Physical Sciences) and the Arts. He has been the coordinator and legal entity head of OpenAIRE, which implements the European policies on open access to research publications and data. He is the software director of the European Human Brain Project flagship initiative, the coordinator of the EOSC Future strategic project, which implements the core elements of the European Open Science Cloud, and a coordinator or partner in tens of other European and national research and innovation projects. He has also led or is currently leading the creation of new international or spin-off companies. He is an ACM and IEEE Fellow, a member of Academia Europaea, and a recipient of several research and teaching awards. He has been the Greek delegate to the European Strategy Forum on Research Infrastructures (ESFRI) for more than 10 years and a co-chair of the Global Climate Hub of the UN Sustainable Development Solutions Network (UN SDSN).