About Bipolar Division Operators

摘要

Introducing preferences inside user queries has gained more and more acceptance during the last decade. However, it turns out that the concept of bipolarity is of interest for expressing queries in the sense that some requirements are mandatory and play the role of constraints, whereas other are solely desirable. In this paper, we investigate how bipolarity may impact the division operator in the context of relational databases. Various forms of bipolar divisions can indeed be devised, each of them conveying a specific semantics.