Journal of the ACM (JACM)
A threshold of ln n for approximating set cover
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
Annotation propagation revisited for key preserving views
CIKM '06 Proceedings of the 15th ACM international conference on Information and knowledge management
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 conjunctive views in deletion propagation
Proceedings of the thirtieth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Maximizing a Monotone Submodular Function Subject to a Matroid Constraint
SIAM Journal on Computing
Multi-tuple deletion propagation: approximations and complexity
Proceedings of the VLDB Endowment
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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 article studies the complexity of deletion propagation, 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 straightforward algorithm, which is called here the unidimensional algorithm. The article identifies additional cases of CQs where the unidimensional algorithm succeeds, and in contrast, shows that for some other CQs the problem is NP-hard to approximate better than some constant ratio. In fact, it is shown here that among the CQs without self joins, the hard CQs are exactly the ones that the unidimensional algorithm fails on. In other words, the following dichotomy result is proved: for every CQ without self joins, deletion propagation is either APX-hard or solvable (in polynomial time) by the unidimensional algorithm. The article 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 sunflower CQs (i.e., CQs having a sunflower hypergraph) without self joins. The first algorithm, providing the approximation ratio 1 − 1/e, is obtained by formulating the problem at hand as that of maximizing a monotone submodular function subject to a matroid constraint, and then using a known algorithm for such maximization. The second algorithm gives a smaller approximation ratio, 1/2, yet in polynomial time even under combined complexity. Finally, it is shown that self joins can significantly harden approximation in deletion propagation.