First-order under-approximations of consistent query answers

摘要

Consistent Query Answering (CQA) is a principled approach for answering queries on inconsistent databases. The consistent answer to a query q on an inconsistent database db is the intersection of the answers to q on all repairs, where a repair is any consistent database that is maximally close to db. Unfortunately, computing consistent answers under primary key constraints has already exponential data complexity for very simple conjunctive queries, and is therefore completely impracticable.