A Proof Procedure for Data Dependencies
Journal of the ACM (JACM)
Equivalence of datalog queries is undecidable
Journal of Logic Programming
Horn clauses and database dependencies
Journal of the ACM (JACM)
On the complexity of single-rule datalog queries
Information and Computation - Special issue: ICC '99
Generic Model Management: Concepts And Algorithms (Lecture Notes in Computer Science)
Generic Model Management: Concepts And Algorithms (Lecture Notes in Computer Science)
Data exchange: getting to the core
ACM Transactions on Database Systems (TODS) - Special Issue: SIGMOD/PODS 2003
Data exchange: semantics and query answering
Theoretical Computer Science - Database theory
Composing schema mappings: Second-order dependencies to the rescue
ACM Transactions on Database Systems (TODS) - Special Issue: SIGMOD/PODS 2004
Data integration: the teenage years
VLDB '06 Proceedings of the 32nd international conference on Very large data bases
Composition of mappings given by embedded dependencies
ACM Transactions on Database Systems (TODS)
Composing mappings among data sources
VLDB '03 Proceedings of the 29th international conference on Very large data bases - Volume 29
Towards a theory of schema-mapping optimization
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
Generalized schema-mappings: from termination to tractability
Proceedings of the twenty-eighth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Reverse data exchange: coping with nulls
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)
On chase termination beyond stratification
Proceedings of the VLDB Endowment
Inverting schema mappings: bridging the gap between theory and practice
Proceedings of the VLDB Endowment
Normalization and optimization of schema mappings
Proceedings of the VLDB Endowment
Composition with target constraints
Proceedings of the 13th International Conference on Database Theory
Normalization and optimization of schema mappings
The VLDB Journal — The International Journal on Very Large Data Bases
Local transformations and conjunctive-query equivalence
PODS '12 Proceedings of the 31st symposium on Principles of Database Systems
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Recently, two relaxed notions of equivalence of schema mappings have been introduced, which provide more potential of optimizing schema mappings than logical equivalence: data exchange (DE) equivalence and conjunctive query (CQ) equivalence. In this work, we systematically investigate these notions of equivalence for mappings consisting of s-t tgds and target egds and/or target tgds. We prove that both CQ- and DE-equivalence are undecidable and so are some important optimization tasks (like detecting if some dependency is redundant). However, we also identify an important difference between the two notions of equivalence: CQ-equivalence remains undecidable even if the schema mappings consist of s-t tgds and target dependencies in the form of key dependencies only. In contrast, DE-equivalence is decidable for schema mappings with s-t tgds and target dependencies in the form of functional and inclusion dependencies with terminating chase property.