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Pattern Matching in Compressed Text and Images
, 2001
"... Normally compressed data needs to be decompressed before it is processed, but if the compression has been done in the fight way, it is often possible to search the data without having to decompress it, or at least only partially decompress it. The problem can be divided into lossless and lossy c ..."
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Cited by 13 (11 self)
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Normally compressed data needs to be decompressed before it is processed, but if the compression has been done in the fight way, it is often possible to search the data without having to decompress it, or at least only partially decompress it. The problem can be divided into lossless and lossy compression methods, and then in each of these cases the pattern matching can be either exact or inexact. Much work has been reported in the literature on techniques for all of these cases, including algorithms that are suitable for pattern matching for various compression methods, and compression methods designed specifically for pattern matching. This work is surveyed in this paper. The paper also exposes the important relationship between pattern matching and compression, and proposes some performance measures for compressed pattern matching algorithms. Ideas and directions for future work are also described.
Two and Higher Dimensional Pattern Matching in Optimal Expected Time
, 1994
"... Algorithms with optimal expected running time are presented for searching the occurrences of a twodimensional m × m pattern P in a twodimensional n × n text T over an alphabet of size c. The algorithms are based on placing in the text a static grid of test points, determined on ..."
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Cited by 13 (4 self)
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Algorithms with optimal expected running time are presented for searching the occurrences of a twodimensional m &times; m pattern P in a twodimensional n &times; n text T over an alphabet of size c. The algorithms are based on placing in the text a static grid of test points, determined only by n, m and c (not dynamically by earlier test results). Using test strings read from the test points the algorithms eliminate as many potential occurrences of P as possible. The remaining potential occurrences are separately checked for actual occurrences. A suitable choice of the test point set leads to algorithms with expected running time O(n 2 log c m 2 =m 2 ) using the uniform Bernoulli model of randomness. This is shown to be optimal by a generalization of a onedimensional lower bound result by Yao. Experimental results show that the algorithms are efficient in practice, too. The method is also generalized for the k mismatches problem. The resulting algorithm has expected running ti...
Approximate Subset Matching with Don't Cares
"... The Subset Matching problem was recently introduced by Cole and Hariharan. The input of the problem is a text array of n sets totaling s elements and a pattern array of m sets totaling s0 elements. There is a match of the pattern in a text location if every pattern set is a subset of the correspondi ..."
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Cited by 13 (1 self)
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The Subset Matching problem was recently introduced by Cole and Hariharan. The input of the problem is a text array of n sets totaling s elements and a pattern array of m sets totaling s0 elements. There is a match of the pattern in a text location if every pattern set is a subset of the corresponding text set. Subset matching has proven to be a powerful technique and enabled finding an efficient solution to the Tree Matching problem. The subset matching model may prove useful in solving other hard problems, e.g. Swap Matching. In this paper we investigate the complexity of approximate subset matching with "don't care"s. We provide two algorithms for the problem. A randomized algorithm whose complexity is O((s + n + n m s 0)pm log2 m) and a deterministic algorithm whose complexity is O((s + n)ps0 log m).
Patternmatching and rewriting rules for group indexed data structures
 ACM SIGPLAN NOTICES
, 2002
"... In this report, we present a new framework for the definition of various datastructures (including trees and arrays) together with a generic language of filters enabling a rulebased programming style of functions. This framework is implemented in an experimental language called MGS. The underlying ..."
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Cited by 12 (5 self)
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In this report, we present a new framework for the definition of various datastructures (including trees and arrays) together with a generic language of filters enabling a rulebased programming style of functions. This framework is implemented in an experimental language called MGS. The underlying notions funding our framework have a topological nature and make possible to extend the casebased definition of functions found in modern functional languages beyond algebraic datastructures.
Bounded Parallelism in Array Grammars Used for Character Recognition
 Advances in Structural and Syntactical Pattern Recognition (Proceedings of the SSPR'96), volume 1121 of LNCS
, 1996
"... . The aim of this paper is to elaborate the power of cooperation in generating and analysing (handwritten) characters by array grammars. We present various noncontextfree sets of arrays that can be generated in a simple way by cooperating distributed array grammar systems with prescribed teams wor ..."
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Cited by 12 (9 self)
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. The aim of this paper is to elaborate the power of cooperation in generating and analysing (handwritten) characters by array grammars. We present various noncontextfree sets of arrays that can be generated in a simple way by cooperating distributed array grammar systems with prescribed teams working in different modes and show the power of the mechanism of cooperation for picture description and analysis as well as the efficiency of these models where several sets of productions work in parallel on the given sentential form. 1 Introduction Cooperation of agents is a usual strategy for approaching complex problems. This strategy is supposed to increase the total competence of the individual agents working together for solving a common task. The recognition of specific patterns like (handwritten) characters can be seen as such a complex task that might be attacked by several agents working in parallel on the underlying pattern. Moreover, the forming of different teams of specialized...
Resource Allocation Analysis of the Stochastic Diffusion Search
, 1999
"... The Stochastic Diffusion Search (SDS) was developed as a solution to the bestfit search problem. Thus, as a special case it is capable of solving the transform invariant pattern recognition problem. SDS is efficient and, although inherently probabilistic, produces very reliable solutions in widely ..."
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Cited by 11 (2 self)
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The Stochastic Diffusion Search (SDS) was developed as a solution to the bestfit search problem. Thus, as a special case it is capable of solving the transform invariant pattern recognition problem. SDS is efficient and, although inherently probabilistic, produces very reliable solutions in widely ranging search conditions. However, to date a systematic formal investigation of its properties has not been carried out. This thesis addresses this problem. The thesis reports results pertaining to the global convergence of SDS as well as characterising its time complexity. However, the main emphasis of the work, reports on the resource allocation aspect of the Stochastic Diffusion Search operations. The thesis introduces a novel model of the algorithm, generalising an Ehrenfest Urn Model from statistical physics. This approach makes it possible to obtain a thorough characterisation of the response of the algorithm in terms of the parameters describing the search conditions in case of a unique bestfit pattern in the search space. This model is further generalised in order to account for different search conditions: two solutions in the search space and search for a unique solution in a noisy search space. Also an approximate solution in the case of two alternative solutions is proposed and compared with predictions
Exploiting symmetry on parallel architectures
, 1995
"... This thesis describes techniques for the design of parallel programs that solvewellstructured problems with inherent symmetry. Part I demonstrates the reduction of such problems to generalized matrix multiplication by a groupequivariant matrix. Fast techniques for this multiplication are described ..."
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Cited by 9 (1 self)
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This thesis describes techniques for the design of parallel programs that solvewellstructured problems with inherent symmetry. Part I demonstrates the reduction of such problems to generalized matrix multiplication by a groupequivariant matrix. Fast techniques for this multiplication are described, including factorization, orbit decomposition, and Fourier transforms over nite groups. Our algorithms entail interaction between two symmetry groups: one arising at the software level from the problem's symmetry and the other arising at the hardware level from the processors' communication network. Part II illustrates the applicability of our symmetryexploitation techniques by presenting a series of case studies of the design and implementation of parallel programs. First, a parallel program that solves chess endgames by factorization of an associated dihedral groupequivariant matrix is described. This code runs faster than previous serial programs, and discovered a number of results. Second, parallel algorithms for Fourier transforms for nite groups are developed, and preliminary parallel implementations for group transforms of dihedral and of symmetric groups are described. Applications in learning, vision, pattern recognition, and statistics are proposed. Third, parallel implementations solving several computational science problems are described, including the direct nbody problem, convolutions arising from molecular biology, and some communication primitives such as broadcast and reduce. Some of our implementations ran orders of magnitude faster than previous techniques, and were used in the investigation of various physical phenomena.
Multidimensional Pattern Matching: A Survey
, 1992
"... We review some recent algorithms motivated by computer vision. The problem inspiring this research is that of searching an aerial photograph for all appearances of some object. The issues we discuss are local errors, scaling, compression and dictionary matching. We review deterministic serial te ..."
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We review some recent algorithms motivated by computer vision. The problem inspiring this research is that of searching an aerial photograph for all appearances of some object. The issues we discuss are local errors, scaling, compression and dictionary matching. We review deterministic serial techniques that are used for multidimensional pattern matching and discuss their strengths and weaknesses. College of Computing Georgia Institute of Technology Atlanta, Georgia 303320280 Paritally supported by NSF grant IRI9013055. 1 Motivation String Matching is one of the most widely studied problems in computer science [Gal85]. Part of its appeal is in its direct applicability to "real world" problems. The KnuthMorrisPratt [KMP77] algorithm is directly implemented in the emacs "s" and UNIX "grep" commands. The longest common subsequence dynamic programming algorithm [CKK72] is implemented in the UNIX "diff" command. The largest overlap heuristic for finding the shortest common s...
New Models and Algorithms for Multidimensional Approximate Pattern Matching
 J. Discret. Algorithms
, 2000
"... We focus on how to compute the edit distance (or similarity) between two images and the problem of approximate string matching in two dimensions, that is, to find a pattern of size mm in a text of size n n with at most k errors (character substitutions, insertions and deletions). Pattern and text a ..."
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Cited by 7 (6 self)
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We focus on how to compute the edit distance (or similarity) between two images and the problem of approximate string matching in two dimensions, that is, to find a pattern of size mm in a text of size n n with at most k errors (character substitutions, insertions and deletions). Pattern and text are matrices over an alphabet of size . We present new models and give the first sublinear time search algorithms for the new and the existing models.
3DList: A Data Structure for Efficient Video Query Processing
 IEEE Transactions on Knowledge and Data Engineering
, 2002
"... In this paper, a video query model based on the content of video and iconic indexing is proposed. We extend the notion of twodimensional strings to threedimensional strings (3DStrings) for representing the spatial and temporal relationships among the symbols in both a video and a video query. The ..."
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In this paper, a video query model based on the content of video and iconic indexing is proposed. We extend the notion of twodimensional strings to threedimensional strings (3DStrings) for representing the spatial and temporal relationships among the symbols in both a video and a video query. The problem of video query processing is then transformed into a problem of threedimensional pattern matching. To efficiently match the 3DStrings, a data structure called 3DList and its related algorithms are proposed. In this approach, the symbols of a video in the video database are retrieved from the video index and organized as a 3DList according to the 3DString of the video query. The related algorithms are then applied on the 3DList to determine whether this video is an answer to the video query. Based on this approach, we have started a project called Vega. In this project, we have implemented a user friendly interface for specifying video queries, a video index tool for constructing the video index, and a video query processor based on the notion of 3DList. Some experiments are also performed to show the efficiency and effectiveness of the proposed algorithms. 1.