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Optimization Properties for Classes of Conjunctive Regular Path Queries
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Generic Model Management: Concepts And Algorithms (Lecture Notes in Computer Science)
Generic Model Management: Concepts And Algorithms (Lecture Notes in Computer Science)
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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
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Composing schema mappings: Second-order dependencies to the rescue
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Proceedings of the twenty-fifth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Composing mappings among data sources
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Model management 2.0: manipulating richer mappings
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Quasi-inverses of schema mappings
ACM Transactions on Database Systems (TODS)
The recovery of a schema mapping: bringing exchanged data back
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On the complexity of deriving schema mappings from database instances
Proceedings of the twenty-seventh ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Towards a theory of schema-mapping optimization
Proceedings of the twenty-seventh ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Answering aggregate queries in data exchange
Proceedings of the twenty-seventh ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Graceful database schema evolution: the PRISM workbench
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Automating database schema evolution in information system upgrades
Proceedings of the 2nd International Workshop on Hot Topics in Software Upgrades
Schema mapping discovery from data instances
Journal of the ACM (JACM)
Inverting schema mappings: bridging the gap between theory and practice
Proceedings of the VLDB Endowment
A Strategy to Revise the Constraints of the Mediated Schema
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Foundations of schema mapping management
Proceedings of the twenty-ninth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Tuning the ensemble selection process of schema matchers
Information Systems
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
Update rewriting and integrity constraint maintenance in a schema evolution support system: PRISM++
Proceedings of the VLDB Endowment
Data exchange beyond complete data
Proceedings of the thirtieth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Automating the database schema evolution process
The VLDB Journal — The International Journal on Very Large Data Bases
Data exchange beyond complete data
Journal of the ACM (JACM)
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Schema mappings are high-level specifications that describe the relationship between two database schemas. Two operators on schema mappings, namely the composition operator and the inverse operator, are regarded as especially important. Progress on the study of the inverse operator was not made until very recently, as even finding the exact semantics of this operator turned out to be a fairly delicate task. Furthermore, this notion is rather restrictive, since it is rare that a schema mapping possesses an inverse. In this paper, we introduce and study the notion of a quasi-inverse of a schema mapping. This notion is a principled relaxation of the notion of an inverse of a schema mapping; intuitively, it is obtained from the notion of an inverse by not differentiating between instances that are equivalent for data-exchange purposes. For schema mappings specified by source-to-target tuple-generating dependencies (s-t tgds), we give a necessary and sufficient combinatorial condition for the existence of a quasi-inverse, and then use this condition to obtain both positive and negative results about the existence of quasi-inverses. In particular, we show that every LAV (local-as-view) schema mappinghas a quasi-inverse, but that there are schema mappings specified by full s-t tgds that have no quasi-inverse. After this, we study the language needed to express quasi-inverses of schema mappings specifiedby s-t tgds, and we obtain a complete characterization. We also characterize the language needed to express inverses of schema mappings, and thereby solve a problem left open in the earlier study of the inverse operator. Finally, we show that quasi-inverses can be used in many cases to recover the data that was exported by the original schemamapping when performing data exchange.