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The boolean hierarchy of k-partitions over NP for k ≥ 3 was introduced as a generalization of the well-known boolean hierarchy of sets (2-partitions). The classes of this hierarchy are exactly those classes of NP-partitions which are generated by finite labeled lattices. We generalize the boolean hierarchy of NP-partitions by studying partition classes(More)
We present dichotomy theorems regarding the computational complexity of counting fixed points in boolean (discrete) dynamical systems, i.e., finite discrete dynamical systems over the domain {0, 1}. For a class F of boolean functions and a class G of graphs, an (F ,G)-system is a boolean dynamical system with local transitions functions lying in F and(More)
In this paper, we study the problem of finding a periodic attractor of a Boolean network (BN), which arises in computational systems biology and is known to be NP-hard. Since a general case is quite hard to solve, we consider special but biologically important subclasses of BNs. For finding an attractor of period 2 of a BN consisting of n OR functions of(More)
We study the complexity of finding a subgraph of a certain size and a certain density, where density is measured by the average degree. Let γ : N → Q+ be any density function, i.e., γ is computable in polynomial time and satisfies γ(k) ≤ k − 1 for all k ∈ N. Then γ-Cluster is the problem of deciding, given an undirected graph G and a natural number k,(More)
An experimental study of the feasibility and accuracy of the acyclicity approach introduced in [14] for the inference of business relationships among autonomous systems (ASes) is provided. We investigate the maximum acyclic type-of-relationship problem: on a given set of AS paths, find a maximum-cardinality subset which allows an acyclic and valley-free(More)