Snapshot semantics is widely used for evaluating queries over temporal data: temporal relations are seen as sequences of snapshot relations, and queries are evaluated at each snapshot. In this work, we demonstrate that current approaches for snapshot semantics over interval-timestamped multiset relations are subject to two bugs regarding snapshot aggregation and bag difference. We introduce a novel temporal data model based on K-relations that overcomes these bugs and prove it to correctly encode snapshot semantics. Furthermore, we present an efficient implementation of our model as a database middleware and demonstrate experimentally that our approach is competitive with native implementations.
@article{DG19, author = {Dign\"{o}s, Anton and Glavic, Boris and Niu, Xing and B\"{o}hlen, Michael H. and Gamper, Johann}, journal = {Proceedings of the VLDB Endowment}, keywords = {Temporal Databases; Annotations}, longversionurl = {https://arxiv.org/pdf/1902.04938}, reproducibility = {https://github.com/IITDBGroup/2019-PVLDB-Reproducibility-Snapshot-Semantics-For-Temporal-Multiset-Relations}, projects = {Snapshot Semantics for Temporal Databases}, number = {6}, pages = {639--652}, pdfurl = {http://www.vldb.org/pvldb/vol12/p639-dignoes.pdf}, title = {{Snapshot Semantics for Temporal Multiset Relations}}, venueshort = {PVLDB}, volume = {12}, year = {2019} }