Minerva Elements Records
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ItemRoleVAT: Visual Assessment of Practical Need for Role Based Access Control(IEEE COMPUTER SOC, 2009)
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ItemThe Sensitivity of Latent Dirichlet Allocation for Information Retrieval(SPRINGER-VERLAG BERLIN, 2009)
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ItemPersonalized PageRank for web page prediction based on access time-length and frequency(IEEE COMPUTER SOC, 2007)
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ItemContinuous intersection joins over moving objects(IEEE, 2008)
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ItemPatterns based classifiers(SPRINGER, 2007-03)
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ItemSurvey of network-based defense mechanisms countering the DoS and DDoS problems(ASSOC COMPUTING MACHINERY, 2007-04)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.
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ItemIncremental maintenance of shortest distance and transitive closure in first-order logic and SQL(ASSOC COMPUTING MACHINERY, 2005-09)Given a database, the view maintenance problem is concerned with the efficient computation of the new contents of a given view when updates to the database happen. We consider the view maintenance problem for the situation when the database contains a weighted graph and the view is either the transitive closure or the answer to the all-pairs shortest-distance problem ( APSD ). We give incremental algorithms for APSD , which support both edge insertions and deletions. For transitive closure, the algorithm is applicable to a more general class of graphs than those previously explored. Our algorithms use first-order queries, along with addition (+) and less-than (<) operations ( FO (+,<)); they store O ( n 2 ) number of tuples, where n is the number of vertices, and have AC 0 data complexity for integer weights. Since FO (+,<) is a sublanguage of SQL and is supported by almost all current database systems, our maintenance algorithms are more appropriate for database applications than nondatabase query types of maintenance algorithms.
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ItemRobust Traffic Merging Strategies for Sensor-Enabled Cars Using Time Geography(ACM, 2009)We present two novel merging algorithms that optimize traffic flow on highways, particularly at intersections of ramps and main roads. In our work, cars are equipped with sensors that can detect distance to neighboring cars, and communicate their velocity and acceleration readings with one another. Sensor-enabled cars can locally exchange sensed information about traffic and adapt their behavior much earlier than regular cars. However, the accuracy level of sensors is a major challenge for merging algorithms, because inaccuracies can potentially lead to unsafe merging behaviors. In this paper, we investigate how the accuracy of sensors impacts merging algorithms, and design robust merging algorithms that tolerate sensor errors. Experimental results show that our main proposed merging algorithm, which is based on concepts from time geography, is able to guarantee safe merging while tolerating four times more imprecise positioning information, and can double the road capacity and increase the traffic flow by 25%.