Decidable optimization problems for database logic programs
STOC '88 Proceedings of the twentieth annual ACM symposium on Theory of computing
Recursive queries and context-free graph grammars
Selected papers of the workshop on Deductive database theory
On the equivalence of recursive and nonrecursive datalog programs
PODS '92 Proceedings of the eleventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Equivalence of datalog queries is undecidable
Journal of Logic Programming
On the complexity of equivalence between recursive and nonrecursive Datalog programs
PODS '94 Proceedings of the thirteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Answering queries using templates with binding patterns (extended abstract)
PODS '95 Proceedings of the fourteenth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Answering queries with useful bindings
ACM Transactions on Database Systems (TODS)
On the decidability of containment of recursive datalog queries - preliminary report
PODS '04 Proceedings of the twenty-third ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Decidable containment of recursive queries
Theoretical Computer Science - Database theory
Optimizing Conjunctive Queries over Trees Using Schema Information
MFCS '08 Proceedings of the 33rd international symposium on Mathematical Foundations of Computer Science
Conjunctive Query Containment under Access Limitations
ER '08 Proceedings of the 27th International Conference on Conceptual Modeling
Determining relevance of accesses at runtime
Proceedings of the thirtieth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Querying schemas with access restrictions
Proceedings of the VLDB Endowment
Between tree patterns and conjunctive queries: is there tractability beyond acyclicity?
MFCS'12 Proceedings of the 37th international conference on Mathematical Foundations of Computer Science
Recursive queries on trees and data trees
Proceedings of the 16th International Conference on Database Theory
Flag & check: data access with monadically defined queries
Proceedings of the 32nd symposium on Principles of database systems
The impact of disjunction on query answering under guarded-based existential rules
IJCAI'13 Proceedings of the Twenty-Third international joint conference on Artificial Intelligence
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We reconsider the problem of containment of monadic datalog (MDL) queries in unions of conjunctive queries (UCQs). Prior work has dealt with special cases, but has left the precise complexity characterization open. We begin by establishing a 2EXPTIME lower bound on the MDL/UCQ containment problem, resolving an open problem from the early 90's. We then present a general approach for getting tighter bounds on the complexity, based on analysis of the number of mappings of queries into tree-like instances. We use the machinery to present an important case of the MDL/UCQ containment problem that is in co-NEXPTIME, and a case that is in EXPTIME. We then show that the technique can be used to get a new tight upper bound for containment of tree automata in UCQs. We show that the new MDL/UCQ upper bounds are tight.