This book constitutes the proceedings of the 4th International Conference on Social Informatics, SocInfo 2012, held in Lausanne, Switzerland, in December 2012. The 21 full papers, 18 short papers included in this volume were carefully reviewed and selected from 61 submissions. The papers are organized in topical sections named: social choice mechanisms in the e-society, computational models of social phenomena, social simulation, web mining and its social interpretations, algorithms and protocols inspired by human societies, socio-economic systems and applications, trust, privacy, risk and security in social contexts.

This book constitutes the thoroughly refereed post-conference proceedings of the Satellite Events of the 12th European Conference on the Semantic Web, ESWC 2015, held in Portoroz, Slovenia, in May/June 2015. The volume contains 12 poster and 22 demonstration papers, selected from 50 submissions, as well as 22 best workshop papers selected from 140 papers presented at the 16 workshops that took place at ESWC 2015. The papers cover various aspects of the semantic web.