Showing papers in "Theoretical Computer Science in 2001"

TL;DR: Improved definitions of well-structured transition systems allow many examples of classical systems to be seen as instances of WSTSs and show several new results.

TL;DR: In this article, the authors investigate spectral and geometric properties of the mutation-crossover operator in a genetic algorithm with general-size alphabet and show how the crossover operator enhances the averaging procedure of the genetic algorithm in the random generator phase.

TL;DR: An extended visual cryptography scheme, for an access structure (ΓQual,ΓForb) on a set of n participants, is a technique to encode n images in such a way that when the authors stack together the transparencies associated to participants in any set X∈�Qual they get the secret message with no trace of the original images, but any X∈Γ forb has no information on the shared image.

TL;DR: In this paper, infinite episturmian words which are a natural generalization of Sturmian word to an arbitrary alphabet are studied and they are obtained by a construction due to de LUCA which utilizes the palindrome closure.

TL;DR: In this paper, the authors present a test suite derivation algorithm for black-box conformance testing of timed I/O automata, inspired by the timed automaton model of Alur and Dill, together with a notion of test sequence for this model.

TL;DR: The paper shows that, by an appropriate choice of a rich assertional language, it is possible to extend the utility of symbolic model checking beyond the realm of BDD-represented finite-state systems into the domain of infinite- state systems, leading to a powerful technique for uniform verification of unbounded (parameterized) process networks.

TL;DR: A linear (thereby, sharp) lower bound on degrees of Positivstellensatz calculus refutations over a real field introduced in Grigoriev and Vorobjov is established.

TL;DR: In this paper, a new method for finding all connected maximal common subgraphs in two graphs is presented based on the transformation of the problem into the clique problem, which is based on variants of the Bron-Kerbosch algorithm.

TL;DR: In this article, the authors present tools and concepts designed by physicists to deal with optimization or decision problems in a language accessible for computer scientists and mathematicians, with no prerequisites in physics.

TL;DR: It is shown that the Steiner ratio is 1 4, that is, the minimum spanning tree yields a polynomial-time approximation with performance ratio exactly 4, and there exists a poynomial- time approximation scheme under certain conditions.

TL;DR: In this paper, the authors studied the dial-a-ride problem with a single server and gave a 2.5-competitive algorithm for the case of infinite capacity and a 1.5competitive algorithm with finite capacity.

TL;DR: It is shown how differential equations can serve as a generic tool for analyzing such algorithms by rederiving most of the known lower bounds for random 3-SAT in a simple, uniform manner.

TL;DR: This paper proposes an extension of the simply typed lambda-calculus with iteration and case constructs which preserves the adequacy of higher-order abstract syntax encodings, and views the methodology of LF to be employed effectively in systems based on induction principles, leading to a synthesis of currently incompatible paradigms.

TL;DR: This paper considers the model checking problem for the μ-calculus and shows that it is succinctly equivalent to the non-emptiness problem of finite-state automata on infinite binary trees with the parity acceptance condition.

TL;DR: A pursue-and-evasion game is analyzed, including almost optimal bounds on the number of moves needed to win.

TL;DR: The equivalence problem for deterministic pushdown automata is shown to be decidable and a complete formal system for deducing equivalent pairs of deterministic rational boolean series on the alphabet associated with a dpda M is exhibited.

TL;DR: This paper solves an open question by showing that the problem is NP-complete in the very restricted case in which the sequences are over a binary alphabet and the score is a metric.

TL;DR: The 'frozen development' of coloring random graphs is defined, and theoretical and empirical evidence is given to show that the size of the smallest uncolorable subgraphs of threshold graphs becomes large as the number of nodes in graphs increases.

TL;DR: It is proved that both problems for calculating the Banzhaf power index and the Shapley-Shubik power index for weighted majority games are NP-complete.

TL;DR: A high-order abstract syntax encoding of π -calculus in the higher-order inductive/coinductive-type theories CIC and CC (Co)Ind gives rise to a full-fledged proof editor/proof assistant, which proves formally a substantial chapter of the theory of strong late bisimilarity.

TL;DR: It is proved that a refined version of the RCC5 table has as models all atomless Boolean algebras B with the natural ordering as the “part-of” relation, and that the table is closed under first-order definable relations iff B is homogeneous.

TL;DR: Path coloring in undirected tree networks is shown to be equivalent to edge coloring of multigraphs, which implies a polynomial-time optimal algorithm for trees of constant degree as well as NP -hardness and an approximation algorithm with absolute approximation ratio 4 3 and asymptotic approximation ratio 1.1.

TL;DR: This paper considers a system with at least two processes among which one can crash, and shows that genuine atomic multicast is impossible to solve with failure detectors that are unreliable, i.e., that cannot distinguish crashed processes from correct ones.

TL;DR: The 1rst rigorous results for random (2 + p)-SAT are given, including the following surprising fact: for p ≤ 2/5, with probability 1 - o(1), a random (1 + p) -SAT formula is satisfiable if its 2-SAT subformula is Satisfiable.

TL;DR: This work presents two on-line algorithms for the bin-stretching problem that guarantee a stretching factor of 5/3 for any number m of bins and designs an algorithm whose stretching factor is 1:625 for any m.

TL;DR: Modal logic is proposed to be used as a logic for coalgebras and the relationship of this approach with the coalgebraic logic of Moss is discussed.

TL;DR: It is proved that the competitive ratio of any online algorithm is at least 2.12457, and a lower bound of 2.33246 is shown on the competitive ratios of anyonline algorithm which schedules obliviously.

TL;DR: A process calculus in which processes are run at distributed locations is defined, which provides operators to kill locations, to test the status (dead or alive) of locations, and to spawn processes at remote locations.

TL;DR: A tutorial reconstruction of Hopcroft's algorithm is given focusing on a firm theoretical basis, clear correctness proofs and a well-founded computational analysis that reveals that if the size of the input alphabet m is not fixed, thenHopcroft's original algorithm does not run in time O(mnlogn) as is commonly believed in the literature.

TL;DR: This paper studies problems such as given a discrete time dynamical system of the form x(t + 1)= f(x(t)) and shows that AM-activity and Stability become decidable in dimension 1 for continuous functions.