On the structure of parameterized problems in NP
Information and Computation
Parameterized circuit complexity and the W hierarchy
Theoretical Computer Science
Threshold dominating sets and an improved characterization of W[2]
Theoretical Computer Science
On the complexity of database queries
Journal of Computer and System Sciences
The parameterized complexity of database queries
PODS '01 Proceedings of the twentieth ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Fixed-Parameter Tractability, Definability, and Model-Checking
SIAM Journal on Computing
The complexity of fixed-parameter problems: guest column
ACM SIGACT News
Approximability and Parameterized Complexity of Minmax Values
WINE '08 Proceedings of the 4th International Workshop on Internet and Network Economics
IWPEC'08 Proceedings of the 3rd international conference on Parameterized and exact computation
The parameterized complexity of editing graphs for bounded degeneracy
Theoretical Computer Science
Randomized approximations of parameterized counting problems
IWPEC'06 Proceedings of the Second international conference on Parameterized and Exact Computation
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We give machine characterizations of most parameterized complexity classes, in particular, of W[P], of the classes of the W-hierarchy, and of the A-hierarchy. For example, we characterize W[P] as the class of all parameterized problems decidable by a nondeterministic fixed-parameter tractable algorithm whose number of nondeterministic steps is bounded in terms of the parameter. The machine characterizations suggest the introduction of a hierarchy Wfunc between the W- and the A-hierarchy. We study the basic properties of this hierarchy.