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Size and Treewidth Bounds for Conjunctive Queries
, 2009
"... This paper provides new worstcase bounds for the size and treewith of the result Q(D) of a conjunctive query Q to a database D. We derive bounds for the result size Q(D)  in terms of structural properties of Q, both in the absence and in the presence of keys and functional dependencies. These bou ..."
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Cited by 8 (1 self)
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This paper provides new worstcase bounds for the size and treewith of the result Q(D) of a conjunctive query Q to a database D. We derive bounds for the result size Q(D)  in terms of structural properties of Q, both in the absence and in the presence of keys and functional dependencies
On Low Treewidth Approximations of Conjunctive Queries
"... We recently initiated the study of approximations of conjunctive queries within classes that admit tractable query evaluation (with respect to combined complexity). Those include classes of acyclic, bounded treewidth, or bounded hypertreewidth queries. Such approximations are always guaranteed to ..."
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Cited by 1 (1 self)
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We recently initiated the study of approximations of conjunctive queries within classes that admit tractable query evaluation (with respect to combined complexity). Those include classes of acyclic, bounded treewidth, or bounded hypertreewidth queries. Such approximations are always guaranteed
Conjunctive Query Containment Revisited
, 1998
"... We consider the problems of conjunctive query containment and minimization, which are known to be NPcomplete, and show that these problems can be solved in polynomial time for the class of acyclic queries. We then generalize the notion of acyclicity and define a parameter called query width that ca ..."
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Cited by 117 (0 self)
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generalize those for acyclic queries, and are of practical significance because many queries have small query width compared to their sizes. We show that good bounds on the query width of Q can be obtained using the treewidth of the incidence graph of Q. We then consider the problem of finding an equivalent
On the Tractability of Query Compilation and Bounded Treewidth
, 2012
"... We consider the problem of computing the probability of a Boolean function, which generalizes the model counting problem. Given an OBDD for such a function, its probability can be computed in linear time in the size of the OBDD. In this paper we investigate the connection between treewidth and the s ..."
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Cited by 5 (0 self)
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and the size of the OBDD. Bounded treewidth has proven to be applicable to many graph problems, which are NPhard in general but become tractable on graphs with bounded treewidth. However, it is less well understood how bounded treewidth can be used for the probability computation problem of a Boolean function
When is the evaluation of conjunctive queries tractable
 In Proceedings of the 33rd ACM Symposium on Theory of Computing
, 2001
"... zINRIARocquencourt Abstract The evaluation of conjunctive queries is hard both with respect to its combined complexity (NPcomplete) and its parameterized complexity (W[1]complete). It becomes tractable (PTIME for combined complexity, FPT for parameterized complexity), when the underlying graphs o ..."
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Cited by 42 (5 self)
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of the conjunctive queries have bounded treewidth [2]. We show that, in some sense, this is optimal both with respect to combined and parameterized complexity: For every class C of graphs, the evaluation of all conjunctive queries whose underlying graph is in C is tractable if, and only if, C has bounded treewidth
Efficient Approximations of Conjunctive Queries
"... When finding exact answers to a query over a large database is infeasible, it is natural to approximate the query by a more efficient one that comes from a class with good bounds on the complexity of query evaluation. In this paper we study such approximations for conjunctive queries. These queries ..."
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Cited by 6 (4 self)
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closure properties of classes of conjunctive queries to the existence of approximations. We also show that in many cases, the size of approximations is bounded by the size of the query they approximate. We establish a number of results showing how combinatorial properties of queries affect properties
The parameterized complexity of conjunctive query . . .
, 2005
"... This thesis is an expository treatment of the article “When is the evaluation of conjunctive queries tractable? ” by Grohe, Schwentick and Segoufin [13]. The topic of the article is the tractability of conjunctive queries to structures. In particular, the authors use a graphtheoretic approach to th ..."
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This thesis is an expository treatment of the article “When is the evaluation of conjunctive queries tractable? ” by Grohe, Schwentick and Segoufin [13]. The topic of the article is the tractability of conjunctive queries to structures. In particular, the authors use a graphtheoretic approach
Conjunctive query evaluation by searchtree revisited
 In 10th International Conference on Database Theory (ICDT
, 2005
"... 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 searchtrees. We investigate the question of evaluating conjunctive queries with a timebound guarantee that is measured ..."
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Cited by 3 (0 self)
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that can be nontrivially folded into a conjunctive query of bounded size or bounded treewidth. All our results translate to the context of constraintsatisfaction
Tractable Counting of the Answers to Conjunctive Queries
"... Conjunctive queries (CQs) are one of the most fundamental forms of database queries. In general, the evaluation of CQs is NPcomplete. Consequently, there has been an intensive search for tractable fragments. In this paper, we want to initiate a systematic search for tractable fragments of the count ..."
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Cited by 6 (2 self)
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of the counting problem of CQs, i.e., the problem of counting the answers to a CQ. We prove several new tractability and intractability results by starting with acyclic conjunctive queries and generalising these results to CQs of bounded hypertreewidth.
Tractable Hypergraph Properties for Constraint Satisfaction and Conjunctive Queries
, 2010
"... An important question in the study of constraint satisfaction problems (CSP) is understanding how the graph or hypergraph describing the incidence structure of the constraints influences the complexity of the problem. For binary CSP instances (i.e., where each constraint involves only two variables ..."
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Cited by 31 (4 self)
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, parameterized by the number of variables. In the applications related to database query evaluation, we usually assume that the number of variables is much smaller than the size of the instance, thus parameterization by the number of variables is a meaningful question. The most general known property of H
Results 1  10
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