Fragments of bag relational algebra: Expressiveness and certain answers

作者：

Highlights：

• Database systems are based on bags, but theoretical research focuses on sets

• Classification of relative expressive power of bag relational algebra fragments

• Complexity of computing certain and possible answers in those fragments.

摘要

•Database systems are based on bags, but theoretical research focuses on sets•Classification of relative expressive power of bag relational algebra fragments•Complexity of computing certain and possible answers in those fragments.

论文关键词：Bag semantics,Relational algebra,Expressiveness,Certain answers,Complexity

论文评审过程：Received 20 November 2019, Revised 1 June 2020, Accepted 17 July 2020, Available online 22 July 2020, Version of Record 24 December 2021.

论文官网地址：https://doi.org/10.1016/j.is.2020.101604