Showing papers in "ACM Computing Surveys in 2007"
TL;DR: The relationship between text entropy and regularities that show up in index structures and permit compressing them are explained and the most relevant self-indexes are covered, focusing on how they exploit text compressibility to achieve compact structures that can efficiently solve various search problems.
Abstract: Full-text indexes provide fast substring search over large text collections. A serious problem of these indexes has traditionally been their space consumption. A recent trend is to develop indexes that exploit the compressibility of the text, so that their size is a function of the compressed text length. This concept has evolved into self-indexes, which in addition contain enough information to reproduce any text portion, so they replace the text. The exciting possibility of an index that takes space close to that of the compressed text, replaces it, and in addition provides fast search over it, has triggered a wealth of activity and produced surprising results in a very short time, which radically changed the status of this area in less than 5 years. The most successful indexes nowadays are able to obtain almost optimal space and search time simultaneously.In this article we present the main concepts underlying (compressed) self-indexes. We explain the relationship between text entropy and regularities that show up in index structures and permit compressing them. Then we cover the most relevant self-indexes, focusing on how they exploit text compressibility to achieve compact structures that can efficiently solve various search problems. Our aim is to give the background to understand and follow the developments in this area.
834 citations
TL;DR: This survey analyzes the design decisions in the Internet that have created the potential for denial of service attacks and the methods that have been proposed for defense against these attacks, and discusses potential countermeasures against each defense mechanism.
Abstract: This article presents a survey of denial of service attacks and the methods that have been proposed for defense against these attacks. In this survey, we analyze the design decisions in the Internet that have created the potential for denial of service attacks. We review the state-of-art mechanisms for defending against denial of service attacks, compare the strengths and weaknesses of each proposal, and discuss potential countermeasures against each defense mechanism. We conclude by highlighting opportunities for an integrated solution to solve the problem of distributed denial of service attacks.
735 citations
TL;DR: This work surveys the current state-of-the-art of information fusion by presenting the known methods, algorithms, architectures, and models, and discusses their applicability in the context of wireless sensor networks.
Abstract: Wireless sensor networks produce a large amount of data that needs to be processed, delivered, and assessed according to the application objectives. The way these data are manipulated by the sensor nodes is a fundamental issue. Information fusion arises as a response to process data gathered by sensor nodes and benefits from their processing capability. By exploiting the synergy among the available data, information fusion techniques can reduce the amount of data traffic, filter noisy measurements, and make predictions and inferences about a monitored entity. In this work, we survey the current state-of-the-art of information fusion by presenting the known methods, algorithms, architectures, and models of information fusion, and discuss their applicability in the context of wireless sensor networks.
606 citations
TL;DR: The purpose of this article is to present these techniques and categorize their characteristics and features in order to assist method selection and promote future research in the area of ontology visualization.
Abstract: Ontologies, as sets of concepts and their interrelations in a specific domain, have proven to be a useful tool in the areas of digital libraries, the semantic web, and personalized information management. As a result, there is a growing need for effective ontology visualization for design, management and browsing. There exist several ontology visualization methods and also a number of techniques used in other contexts that could be adapted for ontology representation. The purpose of this article is to present these techniques and categorize their characteristics and features in order to assist method selection and promote future research in the area of ontology visualization.
469 citations
TL;DR: The article reviews the most popular peer-to-peer key management protocols for mobile ad hoc networks (MANETs) and discusses and provides comments on the strategy of each group separately.
Abstract: The article reviews the most popular peer-to-peer key management protocols for mobile ad hoc networks (MANETs). The protocols are subdivided into groups based on their design strategy or main characteristic. The article discusses and provides comments on the strategy of each group separately. The discussions give insight into open research problems in the area of pairwise key management.
373 citations
TL;DR: A survey of suffix array construction algorithms can be found in this article, with a comparison of the algorithms' worst-case time complexity and use of additional space, together with results of recent experimental test runs on many of their implementations.
Abstract: In 1990, Manber and Myers proposed suffix arrays as a space-saving alternative to suffix trees and described the first algorithms for suffix array construction and use. Since that time, and especially in the last few years, suffix array construction algorithms have proliferated in bewildering abundance. This survey paper attempts to provide simple high-level descriptions of these numerous algorithms that highlight both their distinctive features and their commonalities, while avoiding as much as possible the complexities of implementation details. New hybrid algorithms are also described. We provide comparisons of the algorithms' worst-case time complexity and use of additional space, together with results of recent experimental test runs on many of their implementations.
323 citations
TL;DR: The algorithms underlying various GRNGs are described, their computational requirements are compared, and the quality of the random numbers are examined with emphasis on the behaviour in the tail region of the Gaussian probability density function.
Abstract: Rapid generation of high quality Gaussian random numbers is a key capability for simulations across a wide range of disciplines. Advances in computing have brought the power to conduct simulations with very large numbers of random numbers and with it, the challenge of meeting increasingly stringent requirements on the quality of Gaussian random number generators (GRNG). This article describes the algorithms underlying various GRNGs, compares their computational requirements, and examines the quality of the random numbers with emphasis on the behaviour in the tail region of the Gaussian probability density function.
202 citations
TL;DR: This paper discusses in detail the work principles of the typical RST invariant image watermarking algorithms, analyze the performance of these typical algorithms through implementation and point out their advantages and disadvantages.
Abstract: In this article, we review the algorithms for rotation, scaling and translation (RST) invariant image watermarking. There are mainly two categories of RST invariant image watermarking algorithms. One is to rectify the RST transformed image before conducting watermark detection. Another is to embed and detect watermark in an RST invariant or semi-invariant domain. In order to help readers understand, we first introduce the fundamental theories and techniques used in the existing RST invariant image watermarking algorithms. Then, we discuss in detail the work principles, embedding process, and detection process of the typical RST invariant image watermarking algorithms. Finally, we analyze and evaluate these typical algorithms through implementation, and point out their advantages and disadvantages.
175 citations
TL;DR: The current TA techniques are surveyed, methodology to classify, evaluate, and compare their complexities and efficiencies are provided, and the techniques' advantages and disadvantages are compared.
Abstract: We study and compare topology aggregation techniques used in QoS routing. Topology Aggregation (TA) is defined as a set of techniques that abstract or summarize the state information about the network topology to be exchanged, processed, and maintained by network nodes for routing purposes. Due to scalability, aggregation techniques have been an integral part of some routing protocols. However, TA has not been studied extensively except in a rather limited context. With the continuing growth of the Internet, scalability issues of QoS routing have been gaining importance. Therefore, we survey the current TA techniques, provide methodology to classify, evaluate, and compare their complexities and efficiencies.
75 citations
TL;DR: The quantum-mechanical background needed to present some fundamental protocols from quantum cryptography is provided, and quantum key distribution via the BB84 protocol and its security proof are reviewed.
Abstract: We survey some results in quantum cryptography After a brief introduction to classical cryptography, we provide the quantum-mechanical background needed to present some fundamental protocols from quantum cryptography In particular, we review quantum key distribution via the BB84 protocol and its security proof, as well as the related quantum bit commitment protocol and its proof of insecurity
72 citations
TL;DR: Existing ROLAP methods that implement the data cube are reviewed and six orthogonal parameters/dimensions that characterize them are identified and placed at the appropriate points within the problem space defined by these parameters and several clusters that the techniques form with various interesting properties are identified.
Abstract: Implementation of the data cube is an important and scientifically interesting issue in On-Line Analytical Processing (OLAP) and has been the subject of a plethora of related publications. Naive implementation methods that compute each node separately and store the result are impractical, since they have exponential time and space complexity with respect to the cube dimensionality. To overcome this drawback, a wide range of methods that provide efficient cube implementation (with respect to both computation and storage) have been proposed, which make use of relational, multidimensional, or graph-based data structures. Furthermore, there are several other methods that compute and store approximate descriptions of data cubes, sacrificing accuracy for condensation. In this article, we focus on Relational-OLAP (ROLAP), following the majority of the efforts so far. We review existing ROLAP methods that implement the data cube and identify six orthogonal parameters/dimensions that characterize them. We place the existing techniques at the appropriate points within the problem space defined by these parameters and identify several clusters that the techniques form with various interesting properties. A careful study of these properties leads to the identification of particularly effective values for the space parameters and indicates the potential for devising new algorithms with better overall performance.
TL;DR: A taxonomy of autonomous hypertext authoring tools is described, determined by the type and nature of the document analysis it performs, to facilitate the translation of large document collections into functioning hypertexts.
Abstract: Autonomous authoring tools are routinely used to expedite the translation of large document collections into functioning hypertexts. They are also used to add hyperlinks to pre-existing hypertext structures. In this survey we describe a taxonomy of autonomous hypertext authoring tools. The classification of any given system is determined by the type and nature of the document analysis it performs.