A sound and sometimes complete query evaluation algorithm for relational databases with null values
Journal of the ACM (JACM)
Magic sets and other strange ways to implement logic programs (extended abstract)
PODS '86 Proceedings of the fifth ACM SIGACT-SIGMOD symposium on Principles of database systems
Principles of database and knowledge-base systems, Vol. I
Principles of database and knowledge-base systems, Vol. I
On domain independent databases
Foundations of deductive databases and logic programming
Horn tables-an efficient tool for handling incomplete information in databases
PODS '89 Proceedings of the eighth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Integrity = validity + completeness
ACM Transactions on Database Systems (TODS)
Journal of Logic Programming
Finding nonrecursive envelopes for Datalog predicate
PODS '93 Proceedings of the twelfth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
The alternating fixpoint of logic programs with negation
PODS '89 Selected papers of the eighth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
PODS '94 Proceedings of the thirteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Handbook of logic in artificial intelligence and logic programming (vol. 3)
Approximating general logic programs
ILPS '93 Proceedings of the 1993 international symposium on Logic programming
Answering queries using views (extended abstract)
PODS '95 Proceedings of the fourteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Sound and efficient closed-world reasoning for planning
Artificial Intelligence
Models of approximation in databases
Theoretical Computer Science - Special issue: 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
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
Tabling for non-monotonic programming
Annals of Mathematics and Artificial Intelligence
The Semantic Web: The Roles of XML and RDF
IEEE Internet Computing
Approximating Terminological Queries
FQAS '02 Proceedings of the 5th International Conference on Flexible Query Answering Systems
Tableau Techniques for Querying Information Sources through Global Schemas
ICDT '99 Proceedings of the 7th International Conference on Database Theory
Dependency Satisfaction in Databases with Incomplete Information
VLDB '84 Proceedings of the 10th International Conference on Very Large Data Bases
Closed World Databases Opened Through Null Values
VLDB '88 Proceedings of the 14th International Conference on Very Large Data Bases
Obtaining Complete Answers from Incomplete Databases
VLDB '96 Proceedings of the 22th International Conference on Very Large Data Bases
Efficient Reasoning Using the Local Closed-World Assumption
AIMSA '00 Proceedings of the 9th International Conference on Artificial Intelligence: Methodology, Systems, and Applications
On Indefinite Databases and the Closed World Assumption
Proceedings of the 6th Conference on Automated Deduction
The complexity of relational query languages (Extended Abstract)
STOC '82 Proceedings of the fourteenth annual ACM symposium on Theory of computing
ICCV '95 Proceedings of the Fifth International Conference on Computer Vision
Data exchange: getting to the core
ACM Transactions on Database Systems (TODS) - Special Issue: SIGMOD/PODS 2003
Representing and querying XML with incomplete information
ACM Transactions on Database Systems (TODS)
Data exchange and incomplete information
Proceedings of the twenty-fifth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Any-world assumptions in logic programming
Theoretical Computer Science
Update semantics for incomplete databases
VLDB '85 Proceedings of the 11th international conference on Very Large Data Bases - Volume 11
On representing incomplete information in a relational data base
VLDB '81 Proceedings of the seventh international conference on Very Large Data Bases - Volume 7
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
Approximate query answering in locally closed databases
AAAI'07 Proceedings of the 22nd national conference on Artificial intelligence - Volume 1
Approximating OWL-DL ontologies
AAAI'07 Proceedings of the 22nd national conference on Artificial intelligence - Volume 2
On the local closed-world assumption of data-sources
LPNMR'05 Proceedings of the 8th international conference on Logic Programming and Nonmonotonic Reasoning
Representation of partial knowledge and query answering in locally complete databases
LPAR'06 Proceedings of the 13th international conference on Logic for Programming, Artificial Intelligence, and Reasoning
An approximative inference method for solving ∃¬so satisfiability problems
JELIA'10 Proceedings of the 12th European conference on Logics in artificial intelligence
Checking query completeness over incomplete data
Proceedings of the 4th International Workshop on Logic in Databases
SDKB'10 Proceedings of the 4th international conference on Semantics in data and knowledge bases
An approximative inference method for solving ∃∀SO satisfiability problems
Journal of Artificial Intelligence Research
Constraint Propagation for First-Order Logic and Inductive Definitions
ACM Transactions on Computational Logic (TOCL)
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The Closed World Assumption (CWA) on databases expresses the assumption that an atom not in the database is false. This assumption is applicable only in cases where the database has complete knowledge about the domain of discourse. In this article, we investigate locally closed databases, that is: databases that are sound but partially incomplete about their domain. Such databases consist of a standard database instance, augmented with a collection of Local Closed World Assumptions (LCWAs). A LCWA is a “local” form of the CWA, expressing that a database relation is complete in a certain area, called a window of expertise. In this work, we study locally closed databases both from a knowledge representation and from a computational perspective. At the representation level, the approach taken in this article distinguishes between the data that is conveyed by a database and the metaknowledge about the area in which the data is complete. We study the semantics of the LCWA's and relate it to several knowledge representation formalisms. At the reasoning level, we study the complexity of, and algorithms for two basic reasoning tasks: computing certain and possible answers to queries and determining whether a database has complete knowledge on a query. As the complexity of these tasks is unacceptably high, we develop efficient approximate methods for query answering. We also prove that for useful classes of queries and locally closed databases, these methods are optimal, and thus they solve the original query in a tractable way. As a result, we obtain classes of queries and locally closed databases for which query answering is tractable.