Reconstructing Repairs of Census Data Forms as Database Repairs

In the context of consistent query answering (CQA) from inconsistent databases, the notion of repair is fundamental. A repair is a new database instance that minimally differs from the original, inconsistent database, but does satisfy the integrity constraints. Minimality usually refers to a minimal set of tuples on which the two instances differ. In this paper we reexamine the process of correcting census data forms, where the notion of minimal number of changes is natural. Underlying assumptions are made explicit, and on the basis of this, corrections of census questionnaires are characterised as database repairs as introduced in the context of CQA. Minimal number of changes on census questionnaires are represented as database repairs. Other interesting issues addressed here, that are also relevant in the context of database repairs, are the notions of hard and soft constraints for the repair or correction process, and new specific, but natural ways of minimising changes. Finally, on the basis of the database representation, an answer set programming approach to census questionnaires corrections is presented.