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Reformulation of XML Queries and Constraints
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PODS '04 Proceedings of the twenty-third ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
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
Composing schema mappings: Second-order dependencies to the rescue
ACM Transactions on Database Systems (TODS) - Special Issue: SIGMOD/PODS 2004
Query reformulation with constraints
ACM SIGMOD Record
Nested mappings: schema mapping reloaded
VLDB '06 Proceedings of the 32nd international conference on Very large data bases
ACM Transactions on Database Systems (TODS)
CWA-solutions for data exchange settings with target dependencies
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On reconciling data exchange, data integration, and peer data management
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ACM Transactions on Database Systems (TODS)
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VLDB '03 Proceedings of the 29th international conference on Very large data bases - Volume 29
Update exchange with mappings and provenance
VLDB '07 Proceedings of the 33rd international conference on Very large data bases
Efficient core computation in data exchange
Journal of the ACM (JACM)
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
Towards a theory of schema-mapping optimization
Proceedings of the twenty-seventh ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
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
Data exchange: query answering for incomplete data sources
Proceedings of the 3rd international conference on Scalable information systems
Towards Rule-Based Minimization of RDF Graphs under Constraints
RR '08 Proceedings of the 2nd International Conference on Web Reasoning and Rule Systems
Repair checking in inconsistent databases: algorithms and complexity
Proceedings of the 12th International Conference on Database Theory
Structural characterizations of schema-mapping languages
Proceedings of the 12th International Conference on Database Theory
Querying data sources that export infinite sets of views
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Schema exchange: Generic mappings for transforming data and metadata
Data & Knowledge Engineering
Logical foundations of relational data exchange
ACM SIGMOD Record
Equivalence of SQL queries in presence of embedded dependencies
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Clio: Schema Mapping Creation and Data Exchange
Conceptual Modeling: Foundations and Applications
Automatic schema merging using mapping constraints among incomplete sources
CIKM '10 Proceedings of the 19th ACM international conference on Information and knowledge management
Relaxed notions of schema mapping equivalence revisited
Proceedings of the 14th International Conference on Database Theory
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Journal of the ACM (JACM)
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Database support for enabling data-discovery queries over semantically-annotated observational data
Transactions on Large-Scale Data- and Knowledge-Centered Systems VI
Query processing under GLAV mappings for relational and graph databases
Proceedings of the VLDB Endowment
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
Proceedings of the 22nd ACM international conference on Conference on information & knowledge management
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It is known that the composition of schema mappings, each specified by source-to-target tgds (st-tgds), can be specified by a second-order tgd (SO tgd). We consider the question of what happens when target constraints are allowed. Specifically, we consider the question of specifying the composition of standard schema mappings (those specified by st-tgds, target egds, and a weakly-acyclic set of target tgds). We show that SO tgds, even with the assistance of arbitrary source constraints and target constraints, cannot specify in general the composition of two standard schema mappings. Therefore, we introduce source-to-target second-order dependencies (st-SO dependencies), which are similar to SO tgds, but allow equations in the conclusion. We show that st-SO dependencies (along with target egds and target tgds) are sufficient to express the composition of every finite sequence of standard schema mappings, and further, every st-SO dependency specifies such a composition. In addition to this expressive power, we show that st-SO dependencies enjoy other desirable properties. In particular, they have a polynomial-time chase that generates a universal solution. This universal solution can be used to find the certain answers to unions of conjunctive queries in polynomial time. It is easy to show that the composition of an arbitrary number of standard schema mappings is equivalent to the composition of only two standard schema mappings. We show that surprisingly, the analogous result holds also for schema mappings specified by just st-tgds (no target constraints). That is, the composition of an arbitrary number of such schema mappings is equivalent to the composition of only two such schema mappings. This is proven by showing that every SO tgd is equivalent to an unnested SO tgd (one where there is no nesting of function symbols). The language of unnested SO tgds is quite natural, and we show that unnested SO tgds are capable of specifying the composition of an arbitrary number of schema mappings, each specified by st-tgds. Similarly, we prove unnesting results for st-SO dependencies, with the same types of consequences. The collapsing result for SO tgds gives us two alternative ways to deal with the composition of multiple schema mappings specified by st-tgds. First, we can replace the composition by a single schema mapping, specified by an unnested SO tgd. Second, we can replace the composition by the composition of only two schema mappings, each specified by st-tgds. A similar comment holds for the composition of standard schema mappings.