Robbers, marshals, and guards: game theoretic and logical characterizations of hypertree width
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The Robber and Marshals game is defined, and it is proved that a hypergraph H has hypertree width at most k if and only if k marshals have a winning strategy on H, allowing them to trap a robber who moves along the hyperedges.About:
This article is published in Journal of Computer and System Sciences.The article was published on 2003-06-01 and is currently open access. It has received 135 citations till now. The article focuses on the topics: Conjunctive query & Bounded function.read more
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The complexity of homomorphism and constraint satisfaction problems seen from the other side
TL;DR: It is proved that, under some complexity theoretic assumption from parameterized complexity theory, HOM(C,−) is in polynomial time if and only if C has bounded tree width modulo homomorphic equivalence.
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An annotated bibliography on guaranteed graph searching
TL;DR: This annotated bibliography gives an elementary classification of problems and results related to graph searching and provides a source of bibliographical references on this field.
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Hypertree Decompositions and Tractable Queries
TL;DR: A negative answer is given by proving the NP-completeness of the problem whether for each constant k it can be determined in polynomial time if a query has query-width at most k, and the new concept of hypertree decomposition of a query and the corresponding notion ofhypertree-width is introduced.
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Query evaluation via tree-decompositions
TL;DR: It is shown that the acyclic and bounded tree-width fragments have the same expressive power as the well-known guarded fragment and the finite-variable fragments of first-order logic, respectively.
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Skew strikes back: new developments in the theory of join algorithms
TL;DR: A survey of join algorithms with provable worst-case optimality runtime guarantees can be found in this paper, where the authors provide a simpler and unified description of these algorithms that they hope is useful for theory-minded readers, algorithm designers, and systems implementors.
References
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Book
Foundations of databases
TL;DR: This book discusses Languages, Computability, and Complexity, and the Relational Model, which aims to clarify the role of Semantic Data Models in the development of Query Language Design.
Book
Principles of database and knowledge-base systems
TL;DR: This book goes into the details of database conception and use, it tells you everything on relational databases from theory to the actual used algorithms.
Journal ArticleDOI
Graph minors. II: Algorithmic aspects of tree-width
Neil Robertson,Paul Seymour +1 more
TL;DR: An invariant of graphs called the tree-width is introduced, and used to obtain a polynomially bounded algorithm to test if a graph has a subgraph contractible to H, where H is any fixed planar graph.
Proceedings ArticleDOI
The complexity of relational query languages (Extended Abstract)
TL;DR: The pattern which will be shown is that the expression complexity of the investigated languages is one exponential higher then their data complexity, and for both types of complexity the authors show completeness in some complexity class.