On Some Uses of a Stratified Divisor in an Ordinal Framework

In this paper, we are interested in taking preferences into account for division-like queries. The interest for introducing preferences is first to cope with user needs, then to get discriminated results instead of a flat set of elements. Here, the idea is to use ordinal preferences which are not too demanding for a casual user. Moreover, the type of query considered is inspired by the division operator and some of its variations where preferences apply only to the divisor. The division aims at retrieving the elements associated with a specified set of values and in a similar spirit, the anti-division looks for elements which are associated with none of the values of a given set. One of the focuses of this paper is to investigate queries mixing those two aspects. In order to remain coherent with the denomination of (anti-)division, the property of the result delivered is characterized. Last, a special attention is paid to the implementation of such queries using a regular database management system and some experimental results illustrate the feasibility of the approach.