Advances in databases and information systems 25th European Conference, ADBIS 2021, Tartu, Estonia, August 24-26, 2021 : proceedings - Bellatreche, Ladjel 1968-; Dumas, Marlon 1970-; Karras, Panagiotis; Matulevičius, Raimundas 1976- (Springer, 2021)