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
Optimization Properties for Classes of Conjunctive Regular Path Queries
DBPL '01 Revised Papers from the 8th International Workshop on Database Programming Languages
Generic Model Management: Concepts And Algorithms (Lecture Notes in Computer Science)
Generic Model Management: Concepts And Algorithms (Lecture Notes in Computer Science)
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
Schema mappings, data exchange, and metadata management
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
Composing schema mappings: Second-order dependencies to the rescue
ACM Transactions on Database Systems (TODS) - Special Issue: SIGMOD/PODS 2004
Quasi-inverses of schema mappings
Proceedings of the twenty-sixth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
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
Structural characterizations of schema-mapping languages
Proceedings of the 12th International Conference on Database Theory
Logical foundations of relational data exchange
ACM SIGMOD Record
Reverse data exchange: coping with nulls
Proceedings of the twenty-eighth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Proceedings of the twenty-eighth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Clio: Schema Mapping Creation and Data Exchange
Conceptual Modeling: Foundations and Applications
The recovery of a schema mapping: Bringing exchanged data back
ACM Transactions on Database Systems (TODS)
Composing local-as-view mappings: closure and applications
Proceedings of the 13th International Conference on Database Theory
Composition and inversion of schema mappings
ACM SIGMOD Record
The structure of inverses in schema mappings
Journal of the ACM (JACM)
Proceedings of the 14th International Conference on Database Theory
Reverse data exchange: Coping with nulls
ACM Transactions on Database Systems (TODS)
Classification of annotation semirings over query containment
PODS '12 Proceedings of the 31st symposium on Principles of Database Systems
Core schema mappings: Scalable core computations in data exchange
Information Systems
Query language-based inverses of schema mappings: semantics, computation, and closure properties
The VLDB Journal — The International Journal on Very Large Data Bases
Query processing under GLAV mappings for relational and graph databases
Proceedings of the VLDB Endowment
Ontology evolution without tears
Web Semantics: Science, Services and Agents on the World Wide Web
On simplification of schema mappings
Journal of Computer and System Sciences
The language of plain SO-tgds: Composition, inversion and structural properties
Journal of Computer and System Sciences
Getting unique solution in data exchange
Proceedings of the VLDB Endowment
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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 article, 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 mapping has 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 specified by 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 schema mapping when performing data exchange.