A Proof Procedure for Data Dependencies
Journal of the ACM (JACM)
Incomplete Information in Relational Databases
Journal of the ACM (JACM)
Data integration: a theoretical perspective
Proceedings of the twenty-first ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Foundations of Databases: The Logical Level
Foundations of Databases: The Logical Level
On the complexity of single-rule datalog queries
Information and Computation - Special issue: ICC '99
The complexity of relational query languages (Extended Abstract)
STOC '82 Proceedings of the fourteenth annual ACM symposium on Theory of computing
Elements Of Finite Model Theory (Texts in Theoretical Computer Science. An Eatcs Series)
Elements Of Finite Model Theory (Texts in Theoretical Computer Science. An Eatcs Series)
Composing schema mappings: second-order dependencies to the rescue
PODS '04 Proceedings of the twenty-third ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Locally consistent transformations and query answering in data exchange
PODS '04 Proceedings of the twenty-third ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Data exchange: getting to the core
ACM Transactions on Database Systems (TODS) - Special Issue: SIGMOD/PODS 2003
Schema mappings, data exchange, and metadata management
Proceedings of the twenty-fourth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Data exchange: on the complexity of answering queries with inequalities
Information Processing Letters
Data exchange: semantics and query answering
Theoretical Computer Science - Database theory
The complexity of data exchange
Proceedings of the twenty-fifth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Data exchange and incomplete information
Proceedings of the twenty-fifth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Data exchange in the presence of arithmetic comparisons
EDBT '08 Proceedings of the 11th international conference on Extending database technology: Advances in database technology
Data exchange and schema mappings in open and closed worlds
Proceedings of the twenty-seventh ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Proceedings of the twenty-seventh ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Logical foundations of relational data exchange
ACM SIGMOD Record
Answering non-monotonic queries in relational data exchange
Proceedings of the 13th International Conference on Database Theory
On the tradeoff between mapping and querying power in XML data exchange
Proceedings of the 13th International Conference on Database Theory
Logic and data exchange: which solutions are "good" solutions?
LOFT'08 Proceedings of the 8th international conference on Logic and the foundations of game and decision theory
Data exchange and schema mappings in open and closed worlds
Journal of Computer and System Sciences
ACM Transactions on Database Systems (TODS)
Datalog as a query language for data exchange systems
Datalog'10 Proceedings of the First international conference on Datalog Reloaded
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The class of unions of conjunctive queries (UCQ) has been shown to be particularly well-behaved for data exchange; its certain answers can be computed in polynomial time (in terms of data complexity). However, this is not the only class with this property; the certain answers to any Datalog program can also can be computed in polynomial time. The problem is that both UCQ and Datalog do not allow negated atoms, as adding an unrestricted form of negation to these languages yields to intractability. In this paper, we propose a language called DatalogC(≠) that extends Datalog with a restricted form of negation, and study some of its fundamental properties. In particular, we show that the certain answers to a DatalogC(≠) program can be computed in polynomial time (in terms of data complexity), and that every union of conjunctive queries with at most one inequality or negated relational atom per disjunct, can be efficiently rewritten as a DatalogC(≠) program in the context of data exchange. Furthermore, we show that this is also the case for a syntactic restriction of the class of unions of conjunctive queries with at most two inequalities per disjunct. This syntactic restriction is given by two conditions that are optimal, in the sense that computing certain answers becomes intractable if one removes any of them. Finally, we provide a thorough analysis of the combined complexity of computing certain answers to DatalogC(≠) programs and other related query languages. In particular, we show that this problem is Exptime-complete for DatalogC(≠), even if one restricts to conjunctive queries with single inequalities, which is a fragment of DatalogC(≠) by the result mentioned above. Furthermore, we show that the combined complexity is CoNexptime-complete for the case of conjunctive queries with k inequalities, for every k ≥ 2.