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19
On Similarity Queries for TimeSeries Data: Constraint Specification and Implementation
, 1995
"... Constraints are a natural mechanism for the specification of similarity queries on timeseries data. However, to realize the expressive power of constraint programming in this context, one must provide the matching implementation technology for efficient indexing of very large data sets. In this pap ..."
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Cited by 106 (4 self)
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Constraints are a natural mechanism for the specification of similarity queries on timeseries data. However, to realize the expressive power of constraint programming in this context, one must provide the matching implementation technology for efficient indexing of very large data sets. In this paper, we formalize the intuitive notions of exact and approximate similarity between timeseries patterns and data. Our definition of similarity extends the distance metric used in [2, 7] with invariance under a group of transformations. Our main observation is that the resulting, more expressive, set of constraint queries can be supported by a new indexing technique, which preserves all the desirable properties of the indexing scheme proposed in [2, 7].
Routing in Distributed Networks: Overview and Open Problems
 ACM SIGACT News  Distributed Computing Column
, 2001
"... This article focuses on routing messages in distributed networks with efficient data structures. After an overview of the various results of the literature, we point some interestingly open problems. ..."
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Cited by 51 (13 self)
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This article focuses on routing messages in distributed networks with efficient data structures. After an overview of the various results of the literature, we point some interestingly open problems.
Tighter Lower Bounds on the Exact Complexity of String Matching
, 2002
"... The paper considers the exact number of character comparisons needed to find all occurrences of a pattern of length m in a text of length n using online and general algorithms. For online algorithms, a lower bound of about (1 + ) n character comparisons is obtained. For general algorithms, a lower ..."
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Cited by 14 (4 self)
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The paper considers the exact number of character comparisons needed to find all occurrences of a pattern of length m in a text of length n using online and general algorithms. For online algorithms, a lower bound of about (1 + ) n character comparisons is obtained. For general algorithms, a lower bound of about ) n character comparisons is obtained. These lower bounds complement an online upper bound of about (1 + ) n comparisons obtained recently by Cole and Hariharan. The lower bounds are obtained by finding patterns with interesting combinatorial properties. It is also shown that for some patterns offline algorithms can be more efficient than online algorithms.
An Improved Algorithm for the Membership Problem for Extended Regular Expressions
 In Proceedings of the International Symposium on Mathematical Foundations of Computer Science
, 2002
"... Extended regular expressions (EREs) define regular languages using union, concatenation, repetition, intersection, and complementation operators. The fact ERE allow intersection and complementation makes them exponentially more succinct than regular expression. The membership problem for extended ..."
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Extended regular expressions (EREs) define regular languages using union, concatenation, repetition, intersection, and complementation operators. The fact ERE allow intersection and complementation makes them exponentially more succinct than regular expression. The membership problem for extended regular expressions is to decide, given an expression r and a word w, whether w belongs to the language defined by r. Since regular expressions are useful for describing patterns in strings, the membership problem has numerous applications. In many such applications, the words w are very long and patterns are conveniently described using EREs, making efficient solutions to the membership problem of great practical interest.
On the complexity of computing the capacity of codes that avoid forbidden difference patterns
 IEEE Trans. Inform. Theory
"... Abstract—Some questions related to the computation of the capacity of codes that avoid forbidden difference patterns are analysed. The maximal number of nbit sequences whose pairwise differences do not contain some given forbidden difference patterns is known to increase exponentially with n; the c ..."
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Abstract—Some questions related to the computation of the capacity of codes that avoid forbidden difference patterns are analysed. The maximal number of nbit sequences whose pairwise differences do not contain some given forbidden difference patterns is known to increase exponentially with n; the coefficient of the exponent is the capacity of the forbidden patterns. In this paper, new inequalities for the capacity are given that allow for the approximation of the capacity with arbitrary high accuracy. The computational cost of the algorithm derived from these inequalities is fixed once the desired accuracy is given. Subsequently, a polynomial time algorithm is given for determining if the capacity of a set is positive while the same problem is shown to be NPhard when the sets of forbidden patterns are defined over an extended set of symbols. Finally, the existence of extremal norms is proved for any set of matrices arising in the capacity computation. Based on this result, a second capacity approximating algorithm is proposed. The usefulness of this algorithm is illustrated by computing exactly the capacity of particular codes that were only known approximately. Index Terms—Approximation algorithm, capacity of codes, coding theory, complexity of capacity, joint spectral radius, NPhardness. I.
Efficient Rewriting in Cograph Trace Monoids
 Proc. of the 10th FCT '95, Dresden (Germany) 1995, number 965 in LNCS
, 1995
"... . We consider the basic problem of finding irreducible forms w.r.t. a finite noetherian rewriting system over a free partially commutative monoid where the underlying dependence alphabet is a cograph. A linear time algorithm is developed which determines irreducible normal forms w.r.t. finite, lengt ..."
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Cited by 3 (1 self)
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. We consider the basic problem of finding irreducible forms w.r.t. a finite noetherian rewriting system over a free partially commutative monoid where the underlying dependence alphabet is a cograph. A linear time algorithm is developed which determines irreducible normal forms w.r.t. finite, lengthreducing trace rewriting systems over cograph monoids. This generalizes wellknown results for free monoids and commutative monoids and is a significant improvement to the previously known square time algorithm. 1 Introduction Free partially commutative monoids were introduced in combinatorics by Cartier and Foata [4]. In computer science these monoids are known as trace monoids, cf. Mazurkiewicz [7]. For background material we refer to [1, 8] or [5]. The theory of rewriting over trace monoids combines combinatorial aspects from string rewriting (modulo some commutations) and graph rewriting. The restriction to traces leads to feasible algorithms, but some interesting complexity questions...
On Extended Regular Expressions
"... Abstract. In this paper we extend the work of Campeanu, Salomaa and Yu [1] on extended regular expressions featured in the Unix utility egrep and the popular scripting language Perl. We settle the open issue of closure under intersection and provide an improved pumping lemma that will show that a la ..."
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Abstract. In this paper we extend the work of Campeanu, Salomaa and Yu [1] on extended regular expressions featured in the Unix utility egrep and the popular scripting language Perl. We settle the open issue of closure under intersection and provide an improved pumping lemma that will show that a larger class of languages is not recognizable by extended regular expressions. We also investigate some questions regarding extended multipattern languages introduced by Nagy in [2]. 1
Flexible and Efficient Similarity Querying for Timeseries Data
, 2003
"... We present a flexible and efficient method for similarity querying in timeseries databases. A sequence S is considered similar to a query sequence Q if the sequences match (up to some tolerance ε) after S is appropriately shifted and scaled. Our method allows the user... ..."
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We present a flexible and efficient method for similarity querying in timeseries databases. A sequence S is considered similar to a query sequence Q if the sequences match (up to some tolerance &epsilon;) after S is appropriately shifted and scaled. Our method allows the user...
Parallel String Matching Algorithms
, 1990
"... The string matching problem is one of the most studied problems in computer science. While it is very easily stated and many of the simple algorithms perform very well in practice, numerous works have been published on the subject and research is still very active. In this paper we survey recent ..."
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The string matching problem is one of the most studied problems in computer science. While it is very easily stated and many of the simple algorithms perform very well in practice, numerous works have been published on the subject and research is still very active. In this paper we survey recent results on parallel algorithms for the string matching problem.
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"... the complexity of computing the capacity of codes that avoid forbidden difference patterns ..."
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the complexity of computing the capacity of codes that avoid forbidden difference patterns