Database and expert systems applications 30th international conference, DEXA 2019, Linz, Austria, August 26–29, 2019, proceedings, part I - Hartmann, Sven 1969-; Küng, Josef; Chakravarthy, Sharma; Anderst-Kotsis, Gabriele 1967-; Tjoa, A Min 1952-; Khalil, Ismail 1960- (Lecture notes in computer science, 2019)