Answering queries in categorical databases

Abstract

A compatible categorical data base can be viewed as a single (contingency) table by taking the maximum-entropy extension of the component tables. Such a view, here called universal table model, is needed to answer a user who wishes "cross-classified" categorical data, that is, categorical data resulting from the combination of the information contents of two or more base tables. In order to implement a universal table interface we make use of a query-optimization procedure, which is able to generate an appropriate answer both in the case that the asked data are present in the data base and in the case that they are not and, then, have to be estimated