Incomplete Information in Relational Databases
Journal of the ACM (JACM)
Functional dependencies and constraints on Null values in database relations
Information and Control
On the representation and querying of sets of possible worlds
Selected papers of the workshop on Deductive database theory
Complexity of answering queries using materialized views
PODS '98 Proceedings of the seventeenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Axiomatisation of functional dependencies in incomplete relations
Theoretical Computer Science
On semantic issues connected with incomplete information databases
ACM Transactions on Database Systems (TODS)
The Clio project: managing heterogeneity
ACM SIGMOD Record
Problem of Incomplete Information in Relational Databases
Problem of Incomplete Information in Relational Databases
Data integration: a theoretical perspective
Proceedings of the twenty-first ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Reformulation of XML Queries and Constraints
ICDT '03 Proceedings of the 9th International Conference on Database Theory
Closed World Databases Opened Through Null Values
VLDB '88 Proceedings of the 14th International Conference on Very Large Data Bases
Locally consistent transformations and query answering in data exchange
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
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 exchange and incomplete information
Proceedings of the twenty-fifth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Implementing mapping composition
VLDB '06 Proceedings of the 32nd international conference on Very large data bases
Debugging schema mappings with routes
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)
Model management 2.0: manipulating richer mappings
Proceedings of the 2007 ACM SIGMOD international conference on Management of data
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
VLDB '02 Proceedings of the 28th international conference on Very Large Data Bases
Composing mappings among data sources
VLDB '03 Proceedings of the 29th international conference on Very large data bases - Volume 29
Query languages for data exchange: beyond unions of conjunctive queries
Proceedings of the 12th International Conference on Database Theory
Data exchange: On the complexity of answering queries with inequalities
Information Processing Letters
ACM Transactions on Database Systems (TODS)
Description logic knowledge base exchange
RR'12 Proceedings of the 6th international conference on Web Reasoning and Rule Systems
Value invention in data exchange
Proceedings of the 2013 ACM SIGMOD International Conference on Management of Data
Solutions and query rewriting in data exchange
Information and Computation
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In the study of data exchange one usually assumes an open-world semantics, making it possible to extend instances of target schemas. An alternative closed-world semantics only moves 'as much data as needed' from the source to the target to satisfy constraints of a schema mapping. It avoids some of the problems exhibited by the open-world semantics, but limits the expressivity of schema mappings. Here we propose a mixed approach: one can designate different attributes of target schemas as open or closed, to combine the additional expressivity of the open-world semantics with the better behavior of query answering in closed worlds. We define such schema mappings, and show that they cover a large space of data exchange solutions with two extremes being the known open and closed-world semantics. We investigate the problems of query answering and schema mapping composition, and prove two trichotomy theorems, classifying their complexity based on the number of open attributes. We find conditions under which schema mappings compose, extending known results to a wide range of closed-world mappings. We also provide results for restricted classes of queries and mappings guaranteeing lower complexity.