Discrete Mathematics - Algebraic graph theory; a volume dedicated to Gert Sabidussi
A partial k-arboretum of graphs with bounded treewidth
Theoretical Computer Science
On the complexity of database queries
Journal of Computer and System Sciences
On Interpolation and Automatization for Frege Systems
SIAM Journal on Computing
Conjunctive-query containment and constraint satisfaction
Journal of Computer and System Sciences - Special issue on the seventeenth ACM SIGACT-SIGMOD-SIGART symposium on principles of database systems
The Efficiency of Resolution and Davis--Putnam Procedures
SIAM Journal on Computing
Conjunctive Query Containment Revisited
ICDT '97 Proceedings of the 6th International Conference on Database Theory
Constraint Satisfaction, Bounded Treewidth, and Finite-Variable Logics
CP '02 Proceedings of the 8th International Conference on Principles and Practice of Constraint Programming
The Complexity of Acyclic Conjunctive Queries
FOCS '98 Proceedings of the 39th Annual Symposium on Foundations of Computer Science
Optimal implementation of conjunctive queries in relational data bases
STOC '77 Proceedings of the ninth annual ACM symposium on Theory of computing
Simplified and improved resolution lower bounds
FOCS '96 Proceedings of the 37th Annual Symposium on Foundations of Computer Science
Data exchange: getting to the core
ACM Transactions on Database Systems (TODS) - Special Issue: SIGMOD/PODS 2003
Generic expression hardness results for primitive positive formula comparison
ICALP'11 Proceedings of the 38th international conference on Automata, languages and programming - Volume Part II
Generic expression hardness results for primitive positive formula comparison
Information and Computation
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The most natural and perhaps most frequently used method for testing membership of an individual tuple in a conjunctive query is based on searching trees of partial solutions, or search-trees. We investigate the question of evaluating conjunctive queries with a time-bound guarantee that is measured as a function of the size of the optimal search-tree. We provide an algorithm that, given a database D, a conjunctive query Q, and a tuple a, tests whether Q(a) holds in D in time bounded by a polynomial in (sn)^l^o^g^k(sn)^l^o^g^l^o^g^n and n^r, where n is the size of the domain of the database, k is the number of bound variables of the conjunctive query, s is the size of the optimal search-tree, and r is the maximum arity of the relations. In many cases of interest, this bound is significantly smaller than the n^O^(^k^) bound provided by the naive search-tree method. Moreover, our algorithm has the advantage of guaranteeing the bound for any given conjunctive query. In particular, it guarantees the bound for queries that admit an equivalent form that is much easier to evaluate, even when finding such a form is an NP-hard task. Concrete examples include the conjunctive queries that can be non-trivially folded into a conjunctive query of bounded size or bounded treewidth. All our results translate to the context of constraint-satisfaction problems via the well-publicized correspondence between both frameworks.