Optimized Encodings for Consistent Query Answering via ASP from Different Perspectives

A data integration system provides transparent access to different data sources by suitably combining their data, and providing the user with a unified view of them, called global schema. However, source data are generally not under the control of the data integration process, thus integrated data may violate global integrity constraints even in presence of locally-consistent data sources. In this scenario, it may be anyway interesting to retrieve as much consistent information as possible. The process of answering user queries under global constraint violation is called consistent query answering (CQA). Several notions of CQA have been proposed, e.g. depending on whether the information in the database is assumed to be sound or complete. This paper provides a contribution in this setting; it uniforms solutions coming from different perspectives under a common core and provides some optimizations designed to identify and isolate the inefficient part of the computation of consistent answers. The effectiveness of the approach is evidenced by experimental results reported in the paper.