Consistent Answers to Aggregate Queries

Abstract

In this chapter, we focus our attention on the evaluation of queries of a form different from that considered in the previous chapters. Specifically, we address the problem of evaluating aggregate queries over data inconsistent w.r.t. aggregate constraints, and introduce a technique for providing range-consistent answers of these queries. The range-consistent answer of an aggregate query is the narrowest interval containing all the answers of the query evaluated on every possible repaired database. Three types of aggregate queries are investigated, namely SUM, MIN, and MAX queries. Similarly to the approach described in the previous chapter for computing card-minimal repairs, the technique presented here is based on a translation to the Mixed Integer Linear Programming (MILP) problem, thus enabling wellestablished techniques for MILP resolution to be exploited for computing rangeconsistent answers.