Consistent Query Answering for Atemporal Constraints over Temporal Databases

Abstract

Consistent query answering is a principled approach to query answering on inconsistent databases: when an inconsistent database has more than one plausible repair, queries are answered by returning the intersection of the query answers over all repairs. In this paper, we study consistent query answering over temporal databases relative to atemporal integrity constraints. A temporal database is conceptually viewed as a sequence of atemporal snapshot databases indexed by time. Two approaches to repairing are presented. In the first approach, each snapshot database is repaired individually and independently of earlier or later snapshots. This independence between snapshots facilitates the computation of consistent query answers. A second approach, which is seemingly more realistic, favors the persistence of attribute values in repairs.