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» Tractable hypergraph properties for constraint satisfaction ...
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PODS
2007
ACM
159views Database» more  PODS 2007»
14 years 11 months ago
Generalized hypertree decompositions: np-hardness and tractable variants
The generalized hypertree width GHW(H) of a hypergraph H is a measure of its cyclicity. Classes of conjunctive queries or constraint satisfaction problems whose associated hypergr...
Georg Gottlob, Thomas Schwentick, Zoltán Mi...
TALG
2010
110views more  TALG 2010»
13 years 9 months ago
Approximating fractional hypertree width
Fractional hypertree width is a hypergraph measure similar to tree width and hypertree width. Its algorithmic importance comes from the fact that, as shown in previous work [14], ...
Dániel Marx
FOCS
2003
IEEE
14 years 4 months ago
The Complexity of Homomorphism and Constraint Satisfaction Problems Seen from the Other Side
We give a complexity theoretic classification of homomorphism problems for graphs and, more generally, relational structures obtained by restricting the left hand side structure ...
Martin Grohe