Journal of the ACM (JACM)
Combining fuzzy information from multiple systems
Journal of Computer and System Sciences
Learning dictionaries for information extraction by multi-level bootstrapping
AAAI '99/IAAI '99 Proceedings of the sixteenth national conference on Artificial intelligence and the eleventh Innovative applications of artificial intelligence conference innovative applications of artificial intelligence
Update semantics of relational views
ACM Transactions on Database Systems (TODS)
On the correct translation of update operations on relational views
ACM Transactions on Database Systems (TODS)
On the Desirability of Acyclic Database Schemes
Journal of the ACM (JACM)
Degrees of acyclicity for hypergraphs and relational database schemes
Journal of the ACM (JACM)
PODS '85 Proceedings of the fourth ACM SIGACT-SIGMOD symposium on Principles of database systems
On propagation of deletions and annotations through views
Proceedings of the twenty-first ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
On the semantics of updates in databases
PODS '83 Proceedings of the 2nd ACM SIGACT-SIGMOD symposium on Principles of database systems
Inclusion dependencies and their interaction with functional dependencies
PODS '82 Proceedings of the 1st ACM SIGACT-SIGMOD symposium on Principles of database systems
On the computation of relational view complements
ACM Transactions on Database Systems (TODS)
A 7/8-Approximation Algorithm for MAX 3SAT?
FOCS '97 Proceedings of the 38th Annual Symposium on Foundations of Computer Science
The complexity of relational query languages (Extended Abstract)
STOC '82 Proceedings of the fourteenth annual ACM symposium on Theory of computing
Optimal aggregation algorithms for middleware
Journal of Computer and System Sciences - Special issu on PODS 2001
Hardness of Max 3SAT with No Mixed Clauses
CCC '05 Proceedings of the 20th Annual IEEE Conference on Computational Complexity
Annotation propagation revisited for key preserving views
CIKM '06 Proceedings of the 15th ACM international conference on Information and knowledge management
Maximizing a Submodular Set Function Subject to a Matroid Constraint (Extended Abstract)
IPCO '07 Proceedings of the 12th international conference on Integer Programming and Combinatorial Optimization
Midas: integrating public financial data
Proceedings of the 2010 ACM SIGMOD International Conference on Management of data
The complexity of causality and responsibility for query answers and non-answers
Proceedings of the VLDB Endowment
Automatic rule refinement for information extraction
Proceedings of the VLDB Endowment
Maximizing a Monotone Submodular Function Subject to a Matroid Constraint
SIAM Journal on Computing
A dichotomy in the complexity of deletion propagation with functional dependencies
PODS '12 Proceedings of the 31st symposium on Principles of Database Systems
Maximizing Conjunctive Views in Deletion Propagation
ACM Transactions on Database Systems (TODS)
Provenance-based dictionary refinement in information extraction
Proceedings of the 2013 ACM SIGMOD International Conference on Management of Data
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In deletion propagation, tuples from the database are deleted in order to reflect the deletion of a tuple from the view. Such an operation may result in the (often necessary) deletion of additional tuples from the view, besides the intentionally deleted one. The complexity of deletion propagation is studied, where the view is defined by a conjunctive query (CQ), and the goal is to maximize the number of tuples that remain in the view. Buneman et al. showed that for some simple CQs, this problem can be solved by a trivial algorithm. This paper identifies additional cases of CQs where the trivial algorithm succeeds, and in contrast, it proves that for some other CQs the problem is NP-hard to approximate better than some constant ratio. In fact, this paper shows that among the CQs without self joins, the hard CQs are exactly the ones that the trivial algorithm fails on. In other words, for every CQ without self joins, deletion propagation is either APX-hard or solvable by the trivial algorithm. The paper then presents approximation algorithms for certain CQs where deletion propagation is APX-hard. Specifically, two constant-ratio (and polynomial-time) approximation algorithms are given for the class of star CQs without self joins. The first algorithm is a greedy algorithm, and the second is based on randomized rounding of a linear program. While the first algorithm is more efficient, the second one has a better approximation ratio. Furthermore, the second algorithm can be extended to a significant generalization of star CQs. Finally, the paper shows that self joins can have a major negative effect on the approximability of the problem.