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Item type:Publication, Access status: without files , A self-stabilizing algorithm for edge monitoring in wireless sensor networksSelf-monitoring is a simple and effective mechanism for surveilling wireless sensor networks, especially to cope against faulty or compromised nodes. A node v can monitor the communication over a link e if both end-nodes of e are neighbors of v. Finding a set of monitoring nodes satisfying all monitoring constraints is called the edge-monitoring problem. The minimum edge-monitoring problem is known to be NP-complete. In this paper, we present a novel self-stabilizing algorithm for computing a minimal edge-monitoring set under the unfair distributed scheduler. For sparse networks the time complexity of this new algorithm is much lower than the currently best known algorithm.Publicationtype: Journal Article118 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Distance constraint satisfaction problems(2016-04-01); ; ; ; We study the complexity of constraint satisfaction problems for templates Γ over the integers where the relations are first-order definable from the successor function. In the case that Γ is locally finite (i.e., the Gaifman graph of Γ has finite degree), we show that Γ is homomorphically equivalent to a structure with one of two classes of polymorphisms (which we call modular max and modular min) and the CSP for Γ can be solved in polynomial time, or Γ is homomorphically equivalent to a finite transitive structure, or the CSP for Γ is NP-complete. Assuming a widely believed conjecture from finite domain constraint satisfaction (we require the tractability conjecture by Bulatov, Jeavons and Krokhin in the special case of transitive finite templates), this proves that those CSPs have a complexity dichotomy, that is, are either in P or NP-complete.Publicationtype: Journal Article29 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Partially-commutative context-free processes: expressibility and tractabilityBisimulation equivalence is decidable in polynomial time for both sequential and commutative normed context-free processes, known as BPA and BPP, respectively. Despite apparent similarity between the two classes, different algorithmic techniques were used in each case. We provide one polynomial-time algorithm that works in a superclass of both normed BPA and BPP. It is derived in the setting of partially-commutative context-free processes, a new process class introduced in the paper. It subsumes both BPA and BPP and seems to be of independent interest. Expressibility issue of the new class, in comparison with the normed PA class, is also tackled in the paper.Publicationtype: Journal Article42 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Non-interleaving bisimulation equivalences on Basic Parallel ProcessesWe show polynomial time algorithms for deciding hereditary history preserving bisimilarity (in O (n3 log n)) and history preserving bisimilarity (in O (n6)) on the class Basic Parallel Processes. The latter algorithm also decides a number of other non-interleaving behavioural equivalences (e.g., distributed bisimilarity) which are known to coincide with history preserving bisimilarity on this class. The common general scheme of both algorithms is based on a fixpoint characterization of the equivalences for tree-like labelled event structures. The technique for realizing the greatest fixpoint computation in the case of hereditary history preserving bisimilarity is based on the revealed tight relationship between equivalent tree-like labelled event structures. In the case of history preserving bisimilarity, a technique of deciding classical bisimilarity on acyclic Petri nets is used.Publicationtype: Journal Article28