It is our great pleasure to welcome you to the 2021 Workshop on Open Challenges in Online Social Networks - OASIS 2021, held in conjunction with the 2021 ACM Conference on Hypertext and Social Media - ACM HT 2021. The diffusion of Online Social Networks (OSNs) has had a profound effect on the way we interact and a deep impact on society and business. OSNs have helped people to communicate, breaking down the geographical barriers that restricted communication. Through social networks, virtual communication, sharing of information, community participation is possible even among people in uncomfortable conditions. Today, OSNs are one of the main parts of daily life by affecting sociality, but they are also important channels through which information travels faster than ever. Analysis of OSN can help to foresee events to manage critical scenarios. The rapid growth in popularity has opened new challenging problems which involve numerous fields in computer science. These issues have implications on social graph analysis, trust and security, and so on. Moreover, privacy issues and the usage of mobile devices has opened new research fields in the design of decentralised online social networks, which can be considered one of the most important challenges. Furthermore, the current improvement concerning the study and the proposal of new approaches for Social Networks and Media involve not only complex network analysis, and, in particular, the decentralisation of social services, but also the introduction of new AI solutions. |