A Proof Procedure for Data Dependencies
Journal of the ACM (JACM)
Limits to parallel computation: P-completeness theory
Limits to parallel computation: P-completeness theory
Horn clauses and database dependencies
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
The inference problem for template dependencies
PODS '82 Proceedings of the 1st ACM SIGACT-SIGMOD symposium on Principles of database systems
Reformulation of XML Queries and Constraints
ICDT '03 Proceedings of the 9th International Conference on Database Theory
The Implication Problem for Data Dependencies
Proceedings of the 8th Colloquium on Automata, Languages and Programming
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
Data integration under integrity constraints
Information Systems - Special issue: The 14th international conference on advanced information systems engineering (CAiSE*02)
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
Data exchange: getting to the core
ACM Transactions on Database Systems (TODS) - Special Issue: SIGMOD/PODS 2003
XML data exchange: consistency and query answering
Proceedings of the twenty-fourth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Computing cores for data exchange: new algorithms and practical solutions
Proceedings of the twenty-fourth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Composition of mappings given by embedded dependencies
Proceedings of the twenty-fourth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Data exchange: semantics and query answering
Theoretical Computer Science - Database theory
VLDB '02 Proceedings of the 28th international conference on Very Large Data Bases
ACM Transactions on Database Systems (TODS)
Magic Sets and their application to data integration
Journal of Computer and System Sciences
CWA-solutions for data exchange settings with target dependencies
Proceedings of the twenty-sixth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
On reconciling data exchange, data integration, and peer data management
Proceedings of the twenty-sixth 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
The recovery of a schema mapping: bringing exchanged data back
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
Data exchange: query answering for incomplete data sources
Proceedings of the 3rd international conference on Scalable information systems
Query languages for data exchange: beyond unions of conjunctive queries
Proceedings of the 12th International Conference on Database Theory
Logical foundations of relational data exchange
ACM SIGMOD Record
Proceedings of the twenty-eighth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
The recovery of a schema mapping: Bringing exchanged data back
ACM Transactions on Database Systems (TODS)
Answering non-monotonic queries in relational 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
Query answering under non-guarded rules in datalog+/-
RR'10 Proceedings of the Fourth international conference on Web reasoning and rule systems
Chase termination: a constraints rewriting approach
Proceedings of the VLDB Endowment
The complexity of evaluating tuple generating dependencies
Proceedings of the 14th International Conference on Database Theory
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
On the data complexity of consistent query answering
Proceedings of the 15th International Conference on Database Theory
Towards more expressive ontology languages: The query answering problem
Artificial Intelligence
Schema mappings and data exchange for graph databases
Proceedings of the 16th International Conference on Database Theory
Data exchange beyond complete data
Journal of the ACM (JACM)
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Data exchange is the problem of transforming data structured under a source schema into data structured under a target schema in such a way that all constraints of a schema mapping are satisfied. At the heart of data exchange, lies a basic decision problem, called the existence-of-solutions problem: given a source instance, is there a target instance that satisfies the constraints of the schema mapping at hand? Earlier work showed that for schema mappings specified by embedded implicational dependencies, this problem is solvable in polynomial time, assuming that (1) the schema mapping is kept fixed and (2) the constraints of the schema mapping satisfy a certain structural condition, called weak acyclicity.We investigate the effect of these assumptions on the complexity of the existence-of-solutions problem, and show that each one is indispensable in deriving polynomial-time algorithms for this problem. Specifically, using machinery from universal algebra, we show that if the weak acyclicity assumption is relaxed even in a minimal way, then the existence-of-solutions problem becomes undecidable. We also show that if, in addition to the source instance, the schema mapping is part of the input, then the existence-of-solutions problem becomes EXPTIME-complete. Thus, there is a provable exponential gap between the data complexity and the combined complexity of data exchange. Finally, we study restricted classes of schema mappings and develop a comprehensive picture for the combined complexity of the existence-of-solutions problem for these restrictions. In particular, depending on the restriction considered, the combined complexity of this problem turns out to be either EXPTIME-complete or coNP-complete.