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Logic Programs for Consistently Querying Data Integration Systems
We solve the problem of obtaining answers to queries posed to a mediated integration system under the local-as-view paradigm that are consistent wrt to certain global integrity constraints. For this,Expand
Extending Dependencies with Conditions
A class of conditional inclusion dependencies (CINDs), which extends traditional inclusion dependencies by enforcing bindings of semantically related data values, is introduced, and it is shown that the consistency problem for the combination of CINDs and CFDs becomes undecidable. Expand
Complexity and Approximation of Fixing Numerical Attributes in Databases Under Integrity Constraints
A quantitative definition of database fix is introduced, and the complexity of several decision and optimization problems, including DFP, DFP-hardness, but a good approximation algorithm for a relevant special case; and intractability but good approximation for CQA for aggregate queries for one database atom denials (plus built-ins). Expand
Semantically Correct Query Answers in the Presence of Null Values
A precise semantics for IC satisfaction in a database with null values is proposed that is compatible with the way null values are treated in commercial database management systems and a precise notion of repair is introduced that privileges the introduction of null values when repairing foreign key constraints. Expand
Increasing the Expressivity of Conditional Functional Dependencies without Extra Complexity
The paper proposes an extension of CFDs, referred to as extended Conditional Functional Dependencies, and presents an algorithm that approximates the maximum number of eCFDs that are satisfiable, and introduces an incremental SQL technique for detecting eCFD violations in response to database updates. Expand
Efficient Approximation Algorithms for Repairing Inconsistent Databases
This paper focuses on efficient approximation algorithms to obtain a database repair and presents an algorithm that runs in O(n log n) wrt the size of the database and can be applied to database repairs obtained by a minimal number of tuple deletions. Expand
Deductive databases for computing certain and consistent answers from mediated data integration systems
This paper addresses the problem of retrieving certain and consistent answers to queries posed to a mediated data integration system under the local-as-view paradigm with open sources and conjunctive and disjunctive view definitions by implementing a cautious stable model semantics on top of a normal deductive database. Expand
The complexity and approximation of fixing numerical attributes in databases under integrity constraints
A quantitative definition of database repair is introduced, and the complexity of several decision and optimization problems are investigated, including deciding the existence of repairs within a given distance to the original instance and CQA: deciding consistency of answers to simple and aggregate conjunctive queries under different semantics. Expand
Modeling consistency of spatio-temporal graphs
This work introduces a graph-based approach to the representation of evolving entities in space and time by making a distinction between filiation and spatial relationships between entities, while an extended relational database specification implements the spatio-temporal graph model. Expand
Query Answering in Peer-to-Peer Data Exchange Systems
A semantics for peer consistent answers under exchange constraints and trust relationships is introduced and some techniques for obtaining those answers are presented. Expand