The 40th edition of the ACM SIGMOD-SIGACT-SIGAI Symposium on Principles of Database Systems (PODS) was held from June 20 to June 25, 2021, in Xi'an, Shaanxi, China. Due to the COVID-19 pandemic, it was organized in hybrid mode, with a local event primarily targeting the Chinese data management community and as a virtual (on- line) conference for the international community. As in previous years, the symposium was held jointly with the ACM International Conference on Management of Data (SIGMOD). PODS focuses on theoretical aspects of data management systems, and the co-location with SIGMOD stimulates interaction between theory-oriented and system-oriented research.
