Principles of database and knowledge-base systems, Vol. I
Principles of database and knowledge-base systems, Vol. I
Consistent query answers in inconsistent databases
PODS '99 Proceedings of the eighteenth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
On the Structure of Polynomial Time Reducibility
Journal of the ACM (JACM)
On the Desirability of Acyclic Database Schemes
Journal of the ACM (JACM)
Consistent query answering under key and exclusion dependencies: algorithms and experiments
Proceedings of the 14th ACM international conference on Information and knowledge management
First-order query rewriting for inconsistent databases
Journal of Computer and System Sciences
Probabilistic databases: diamonds in the dirt
Communications of the ACM - Barbara Liskov: ACM's A.M. Turing Award Winner
On the consistent rewriting of conjunctive queries under primary key constraints
Information Systems
Minimal-change integrity maintenance using tuple deletions
Information and Computation
Proceedings of the twenty-ninth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
A remark on the complexity of consistent conjunctive query answering under primary key violations
Information Processing Letters
Queries and materialized views on probabilistic databases
Journal of Computer and System Sciences
Probabilistic Databases
A dichotomy in the complexity of consistent query answering for queries with two atoms
Information Processing Letters
First-order query rewriting for inconsistent databases
ICDT'05 Proceedings of the 10th international conference on Database Theory
Certain conjunctive query answering in first-order logic
ACM Transactions on Database Systems (TODS)
Database Repairing and Consistent Query Answering
Database Repairing and Consistent Query Answering
Data complexity of query answering in description logics
Artificial Intelligence
A dichotomy in the complexity of counting database repairs
Journal of Computer and System Sciences
Hi-index | 0.00 |
An uncertain database is defined as a relational database in which primary keys need not be satisfied. A repair (or possible world) of such database is obtained by selecting a maximal number of tuples without ever selecting two distinct tuples with the same primary key value. For a Boolean query q, the decision problem CERTAINTY(q) takes as input an uncertain database db and asks whether q is satisfied by every repair of db. Our main focus is on acyclic Boolean conjunctive queries without self-join. Previous work has introduced the notion of (directed) attack graph of such queries, and has proved that CERTAINTY(q) is first-order expressible if and only if the attack graph of q is acyclic. The current paper investigates the boundary between tractability and intractability of CERTAINTY(q). We first classify cycles in attack graphs as either weak or strong, and then prove among others the following. If the attack graph of a query q contains a strong cycle, then CERTAINTY(q) is coNP-complete. If the attack graph of q contains no strong cycle and every weak cycle is terminal (i.e., no edge leads from a vertex in the cycle to a vertex outside the cycle), then CERTAINTY(q) is in P. We then partially address the only remaining open case, i.e., when the attack graph contains some nonterminal cycle and no strong cycle. Finally, we establish a relationship between the complexities of CERTAINTY(q) and evaluating q on probabilistic databases.