ACM Transactions on Database Systems (TODS)
Consistent query answers in inconsistent databases
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A Logical Framework for Querying and Repairing Inconsistent Databases
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Computing consistent query answers using conflict hypergraphs
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ConQuer: efficient management of inconsistent databases
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ACM Transactions on Computational Logic (TOCL)
Logic programs for consistently querying data integration systems
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Query rewriting and answering under constraints in data integration systems
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First-order query rewriting for inconsistent databases
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ACM SIGMOD Record
Repair localization for query answering from inconsistent databases
ACM Transactions on Database Systems (TODS)
Inconsistency tolerance in P2P data integration: An epistemic logic approach
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Consistent query answering under primary keys: a characterization of tractable queries
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On the consistent rewriting of conjunctive queries under primary key constraints
Information Systems
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Consistent query answers in the presence of universal constraints
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Extended aggregations for databases with referential integrity issues
Data & Knowledge Engineering
Consistent query answering over description logic ontologies
RR'07 Proceedings of the 1st international conference on Web reasoning and rule systems
On the consistent rewriting of conjunctive queries under primary key constraints
DBPL'07 Proceedings of the 11th international conference on Database programming languages
Proceedings of the twenty-ninth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Query rewriting for inconsistent DL-lite ontologies
RR'11 Proceedings of the 5th international conference on Web reasoning and rule systems
Consistent query answering: five easy pieces
ICDT'07 Proceedings of the 11th international conference on Database Theory
On the first-order reducibility of unions of conjunctive queries over inconsistent databases
EDBT'06 Proceedings of the 2006 international conference on Current Trends in Database Technology
Project-Join-Repair: an approach to consistent query answering under functional dependencies
FQAS'06 Proceedings of the 7th international conference on Flexible Query Answering Systems
Certain conjunctive query answering in first-order logic
ACM Transactions on Database Systems (TODS)
Charting the tractability frontier of certain conjunctive query answering
Proceedings of the 32nd symposium on Principles of database systems
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Research in consistent query answering studies the definition and computation of "meaningful" answers to queries posed to inconsistent databases, i.e., databases whose data do not satisfy the integrity constraints (ICs) declared on their schema. Computing consistent answers to conjunctive queries is generally coNP-hard in data complexity, even in the presence of very restricted forms of ICs (single, unary keys). Recent studies on consistent query answering for database schemas containing only key dependencies have analyzed the possibility of identifying classes of queries whose consistent answers can be obtained by a first-order rewriting of the query, which in turn can be easily formulated in SQL and directly evaluated through any relational DBMS. In this paper we study consistent query answering in the presence of key dependencies and exclusion dependencies. We first prove that even in the presence of only exclusion dependencies the problem is coNP-hard in data complexity, and define a general method for consistent answering of conjunctive queries under key and exclusion dependencies, based on the rewriting of the query in Datalog with negation. Then, we identify a subclass of conjunctive queries that can be first-order rewritten in the presence of key and exclusion dependencies, and define an algorithm for computing the first-order rewriting of a query belonging to such a class of queries. Finally, we compare the relative efficiency of the two methods for processing queries in the subclass above mentioned. Experimental results, conducted on a real and large database of the computer science engineering degrees of the University of Rome "La Sapienza", clearly show the computational advantage of the first-order based technique.