Integrating data from possibly inconsistent databases

The author addresses the problem of data inconsistencies while integrating data sets from multiple autonomous relational databases. The author starts by arguing that the semantics of integrating possibly inconsistent data is naturally captured by the maximal consistent subsets of the set of all information contained in the collected data. Based on this idea, a simple and intuitive semantical framework is proposed, called the integrated relational calculus which is an extension of the classical relational calculus, for manipulating and querying possibly inconsistent data. It is then shown that the model generalizes the model of flexible relational algebra of Agarwal, Keller, Wiederhold and Saraswat (1995) in the sense that the latter can be embedded into the former. It is also shown that the flexible relational model is not capable of integrating correctly relations with more than one key. The author further argues that flexible relational model provides a rather weak query language. The author then proves that for databases with only one key the flexible model provides a correct integration of inconsistent data