Consistent Query Answering via ASP from Different Perspectives: Theory and Practice

摘要

A data integration system provides transparent access to different datasources by suitably combining their data, and providing the user with a unifiedview of them, called global schema. However, source data are generally notunder the control of the data integration process, thus integrated data mayviolate global integrity constraints even in presence of locally-consistentdata sources. In this scenario, it may be anyway interesting to retrieve asmuch consistent information as possible. The process of answering user queriesunder global constraint violations is called consistent query answering (CQA).Several notions of CQA have been proposed, e.g., depending on whetherintegrated information is assumed to be sound, complete, exact or a variant ofthem. This paper provides a contribution in this setting: it uniforms solutionscoming from different perspectives under a common ASP-based core, and providesquery-driven optimizations designed for isolating and eliminatinginefficiencies of the general approach for computing consistent answers.Moreover, the paper introduces some new theoretical results enriching existingknowledge on decidability and complexity of the considered problems. Theeffectiveness of the approach is evidenced by experimental results. To appear in Theory and Practice of Logic Programming (TPLP).