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 Resource Type:
 Conference Proceeding
 Creator:
 Oommen, B. John, Zhan, Justin, and Crisostomo, Johanna
 Abstract:
 Anomaly detection involves identifying observations that deviate from the normal behavior of a system. One of the ways to achieve this is by identifying the phenomena that characterize "normal" observations. Subsequently, based on the characteristics of data learned from the normal observations, new observations are classified as being either normal or not. Most stateoftheart approaches, especially those which belong to the family parameterized statistical schemes, work under the assumption that the underlying distributions of the observations are stationary. That is, they assume that the distributions that are learned during the training (or learning) phase, though unknown, are not timevarying. They further assume that the same distributions are relevant even as new observations are encountered. Although such a " stationarity" assumption is relevant for many applications, there are some anomaly detection problems where stationarity cannot be assumed. For example, in network monitoring, the patterns which are learned to represent normal behavior may change over time due to several factors such as network infrastructure expansion, new services, growth of user population, etc. Similarly, in meteorology, identifying anomalous temperature patterns involves taking into account seasonal changes of normal observations. Detecting anomalies or outliers under these circumstances introduces several challenges. Indeed, the ability to adapt to changes in nonstationary environments is necessary so that anomalous observations can be identified even with changes in what would otherwise be classified as normal behavior. In this paper, we proposed to apply weak estimation theory for anomaly detection in dynamic environments. In particular, we apply this theory to detect anomaly activities in system calls. Our experimental results demonstrate that our proposal is both feasible and effective for the detection of such anomalous activities.
 Date Created:
 20120922

 Resource Type:
 Conference Proceeding
 Creator:
 Peng, Mengfei, Shi, Wei, Croft, William Lee, and Corriveau, JeanPierre
 Abstract:
 New threats to networks are constantly arising. This justifies protecting network assets and mitigating the risk associated with attacks. In a distributed environment, researchers aim, in particular, at eliminating faulty network entities. More specifically, much research has been conducted on locating a single static black hole, which is defined as a network site whose existence is known a priori and that disposes of any incoming data without leaving any trace of this occurrence. However, the prevalence of faulty nodes requires an algorithm able to (a) identify faulty nodes that can be repaired without human intervention and (b) locate black holes, which are taken to be faulty nodes whose repair does require human intervention. In this paper, we consider a specific attack model that involves multiple faulty nodes that can be repaired by mobile software agents, as well as a virus v that can infect a previously repaired faulty node and turn it into a black hole. We refer to the task of repairing multiple faulty nodes and pointing out the location of the black hole as the Faulty Node Repair and Dynamically Spawned Black Hole Search. Wefirst analyze the attack model we put forth. We then explain (a) how to identify whether a node is either (1) a normal node or (2) a repairable faulty node or (3) the black hole that has been infected by virus v during the search/repair process and, (b) how to perform the correct relevant actions. These two steps constitute a complex task, which, we explain, significantly differs from the traditional Black Hole Search. We continue by proposing an algorithm to solve this problem in an asynchronous ring network with only one whiteboard (which resides in a node called the homebase). We prove the correctness of our solution and analyze its complexity by both theoretical analysis and experiment evaluation. We conclude that, using our proposed algorithm, b + 4 agents can repair all faulty nodes and locate the black hole infected by a virus v within finite time. Our algorithm works even when the number of faulty nodes b is unknown a priori.
 Date Created:
 20170101

 Resource Type:
 Conference Proceeding
 Creator:
 Guo, Yuhong and Li, Xin
 Abstract:
 Semantic scene classification is a challenging problem in computer vision. In this paper, we present a novel multilevel active learning approach to reduce the human annotation effort for training robust scene classification models. Different from most existing active learning methods that can only query labels for selected instances at the target categorization level, i.e., the scene class level, our approach establishes a semantic framework that predicts scene labels based on a latent objectbased semantic representation of images, and is capable to query labels at two different levels, the target scene class level (abstractive high level) and the latent object class level (semantic middle level). Specifically, we develop an adaptive active learning strategy to perform multilevel label query, which maintains the default label query at the target scene class level, but switches to the latent object class level whenever an "unexpected" target class label is returned by the labeler. We conduct experiments on two standard scene classification datasets to investigate the efficacy of the proposed approach. Our empirical results show the proposed adaptive multilevel active learning approach can outperform both baseline active learning methods and a stateoftheart multilevel active learning method.
 Date Created:
 20140101

 Resource Type:
 Conference Proceeding
 Creator:
 Oommen, B. John and Polk, Spencer
 Abstract:
 The field of game playing is a particularly wellstudied area within the context of AI, leading to the development of powerful techniques, such as the alphabeta search, capable of achieving competitive game play against an intelligent opponent. It is well known that tree pruning strategies, such as alphabeta, benefit strongly from proper move ordering, that is, searching the best element first. Inspired by the formerly unrelated field of Adaptive Data Structures (ADSs), we have previously introduced the HistoryADS technique, which employs an adaptive list to achieve effective and dynamic move ordering, in a domain independent fashion, and found that it performs well in a wide range of cases. However, previous work did not compare the performance of the HistoryADS heuristic to any established move ordering strategy. In an attempt to address this problem, we present here a comparison to two wellknown, acclaimed strategies, which operate on a similar philosophy to the HistoryADS, the History Heuristic, and the Killer Moves technique. We find that, in a wide range of twoplayer and multiplayer games, at various points in the game’s progression, the HistoryADS performs at least as well as these strategies, and, in fact, outperforms them in the majority of cases.
 Date Created:
 20160101

 Resource Type:
 Conference Proceeding
 Creator:
 Oommen, B. John and Astudillo, César A.
 Abstract:
 We present a method that employs a treebased Neural Network (NN) for performing classification. The novel mechanism, apart from incorporating the information provided by unlabeled and labeled instances, rearranges the nodes of the tree as per the laws of Adaptive Data Structures (ADSs). Particularly, we investigate the Pattern Recognition (PR) capabilities of the TreeBased TopologyOriented SOM (TTOSOM) when Conditional Rotations (CONROT) [8] are incorporated into the learning scheme. The learning methodology inherits all the properties of the TTOSOMbased classifier designed in [4]. However, we now augment it with the property that frequently accessed nodes are moved closer to the root of the tree. Our experimental results show that on average, the classification capabilities of our proposed strategy are reasonably comparable to those obtained by some of the stateoftheart classification schemes that only use labeled instances during the training phase. The experiments also show that improved levels of accuracy can be obtained by imposing trees with a larger number of nodes.
 Date Created:
 20150101

 Resource Type:
 Conference Proceeding
 Creator:
 Yazidi, Anis, Oommen, B. John, and Hammer, Hugo Lewi
 Abstract:
 The problem of clustering, or unsupervised classification, has been solved by a myriad of techniques, all of which depend, either directly or implicitly, on the Bayesian principle of optimal classification. To be more specific, within a Bayesian paradigm, if one is to compare the testing sample with only a single point in the feature space from each class, the optimal Bayesian strategy would be to achieve this based on the distance from the corresponding means or central points in the respective distributions. When this principle is applied in clustering, one would assign an unassigned sample into the cluster whose mean is the closest, and this can be done in either a bottomup or a topdown manner. This paper pioneers a clustering achieved in an “AntiBayesian” manner, and is based on the breakthrough classification paradigm pioneered by Oommen et al. The latter relies on a radically different approach for classifying data points based on the noncentral quantiles of the distributions. Surprisingly and counterintuitively, this turns out to work equally or closetoequally well to an optimal supervised Bayesian scheme, which thus begs the natural extension to the unexplored arena of clustering. Our algorithm can be seen as the AntiBayesian counterpart of the wellknown kmeans algorithm (The fundamental AntiBayesian paradigm need not just be used to the kmeans principle. Rather, we hypothesize that it can be adapted to any of the scores of techniques that is indirectly based on the Bayesian paradigm.), where we assign points to clusters using quantiles rather than the clusters’ centroids. Extensive experimentation (This paper contains the prima facie results of experiments done on one and twodimensional data. The extensions to multidimensional data are not included in the interest of space, and would use the corresponding multidimensional AntiNa¨ıveBayes classification rules given in [1].) demonstrates that our AntiBayesian clustering converges fast and with precision results competitive to a kmeans clustering.
 Date Created:
 20150101

 Resource Type:
 Conference Proceeding
 Creator:
 Tavasoli, Hanane, Oommen, B. John, and Yazidi, Anis
 Abstract:
 In this paper, we propose a novel online classifier for complex data streams which are generated from nonstationary stochastic properties. Instead of using a single training model and counters to keep important data statistics, the introduced online classifier scheme provides a realtime selfadjusting learning model. The learning model utilizes the multiplicationbased update algorithm of the Stochastic Learning Weak Estimator (SLWE) at each time instant as a new labeled instance arrives. In this way, the data statistics are updated every time a new element is inserted, without requiring that we have to rebuild its model when changes occur in the data distributions. Finally, and most importantly, the model operates with the understanding that the correct classes of previouslyclassified patterns become available at a later juncture subsequent to some time instances, thus requiring us to update the training set and the training model. The results obtained from rigorous empirical analysis on multinomial distributions, is remarkable. Indeed, it demonstrates the applicability of our method on synthetic datasets, and proves the advantages of the introduced scheme.
 Date Created:
 20160101

 Resource Type:
 Conference Proceeding
 Creator:
 Polk, Spencer and Oommen, B. John
 Abstract:
 This paper pioneers the avenue of enhancing a wellknown paradigm in game playing, namely the use of Historybased heuristics, with a totallyunrelated area of computer science, the field of Adaptive Data Structures (ADSs). It is a wellknown fact that highlyregarded game playing strategies, such as alphabeta search, benefit strongly from proper move ordering, and from this perspective, the History heuristic is, probably, one of the most acclaimed techniques used to achieve AIbased game playing. Recently, the authors of this present paper have shown that techniques derived from the field of ADSs, which are concerned with query optimization in a data structure, can be applied to move ordering in multiplayer games. This was accomplished by ranking opponent threat levels. The work presented in this paper seeks to extend the utility of ADSbased techniques to twoplayer and multiplayer games, through the development of a new move ordering strategy that incorporates the historical advantages of the moves. The resultant technique, the HistoryADS heuristic, has been found to produce substantial (i.e, even up to 70%) savings in a variety of twoplayer and multiplayer games, at varying ply depths, and at both initial and midgame board states. As far as we know, results of this nature have not been reported in the literature before.
 Date Created:
 20150101

 Resource Type:
 Conference Proceeding
 Creator:
 Labiche, Yvan and Barros, Márcio
 Date Created:
 20150101

 Resource Type:
 Conference Proceeding
 Creator:
 Oommen, B. John and Kim, SangWoon
 Abstract:
 This paper deals with the relatively new field of sequencebased estimation which involves utilizing both the information in the observations and in their sequence of appearance. Our intention is to obtain Maximum Likelihood estimates by “extracting” the information contained in the observations when perceived as a sequence rather than as a set. The results of [15] introduced the concepts of Sequence Based Estimation (SBE) for the Binomial distribution. This current paper generalizes these results for the multinomial “twoatatime” scenario. We invoke a novel phenomenon called “Occlusion” that can be described as follows: By “concealing” certain observations, we map the estimation problem onto a lowerdimensional binomial space. Once these occluded SBEs have been computed, we demonstrate how the overall Multinomial SBE (MSBE) can be obtained by mapping several lowerdimensional estimates onto the original higherdimensional space. We formally prove and experimentally demonstrate the convergence of the corresponding estimates.
 Date Created:
 20160101

 Resource Type:
 Conference Proceeding
 Creator:
 Maheshwari, Anil, Nandy, Ayan, Smid, Michiel, and Das, Sandip
 Abstract:
 Consider a line segment R consisting of n facilities. Each facility is a point on R and it needs to be assigned exactly one of the colors from a given palette of c colors. At an instant of time only the facilities of one particular color are 'active' and all other facilities are 'dormant'. For the set of facilities of a particular color, we compute the one dimensional Voronoi diagram, and find the cell, i.e, a segment of maximum length. The users are assumed to be uniformly distributed over R and they travel to the nearest among the facilities of that particular color that is active. Our objective is to assign colors to the facilities in such a way that the length of the longest cell is minimized. We solve this optimization problem for various values of n and c. We propose an optimal coloring scheme for the number of facilities n being a multiple of c as well as for the general case where n is not a multiple of c. When n is a multiple of c, we compute an optimal scheme in Θ(n) time. For the general case, we propose a coloring scheme that returns the optimal in O(n2logn) time.
 Date Created:
 20140101

 Resource Type:
 Conference Proceeding
 Creator:
 Kim, SangWoon and Oommen, B. John
 Abstract:
 The Maximum Likelihood (ML) and Bayesian estimation paradigms work within the model that the data, from which the parameters are to be estimated, is treated as a set rather than as a sequence. The pioneering paper that dealt with the field of sequencebased estimation [2] involved utilizing both the information in the observations and in their sequence of appearance. The results of [2] introduced the concepts of Sequence Based Estimation (SBE) for the Binomial distribution, where the authors derived the corresponding MLE results when the samples are taken twoatatime, and then extended these for the cases when they are processed threeatatime, fouratatime etc. These results were generalized for the multinomial “twoatatime” scenario in [3]. This paper (This paper is dedicated to the memory of Dr. Mohamed Kamel, who was a close friend of the first author.) now further generalizes the results found in [3] for the multinomial case and for subsequences of length 3. The strategy used in [3] (and also here) involves a novel phenomenon called “Occlusion” that has not been reported in the field of estimation. The phenomenon can be described as follows: By occluding (hiding or concealing) certain observations, we map the estimation problem onto a lowerdimensional space, i.e., onto a binomial space. Once these occluded SBEs have been computed, the overall Multinomial SBE (MSBE) can be obtained by combining these lowerdimensional estimates. In each case, we formally prove and experimentally demonstrate the convergence of the corresponding estimates.
 Date Created:
 20160101

 Resource Type:
 Conference Proceeding
 Creator:
 Bertossi, Leopoldo
 Abstract:
 A correspondence between database tuples as causes for query answers in databases and tuplebased repairs of inconsistent databases with respect to denial constraints has already been established. In this work, answerset programs that specify repairs of databases are used as a basis for solving computational and reasoning problems about causes. Here, causes are also introduced at the attribute level by appealing to a both nullbased and attributebased repair semantics. The corresponding repair programs are presented, and they are used as a basis for computation and reasoning about attributelevel causes.
 Date Created:
 20180101

 Resource Type:
 Conference Proceeding
 Creator:
 Dujmović, Vida, De Carufel, JeanLou, Bose, Prosenjit, and Paradis, Frédérik
 Abstract:
 The wellseparated pair decomposition (WSPD) of the complete Euclidean graph defined on points in ℝ2 (Callahan and Kosaraju [JACM, 42 (1): 6790, 1995]) is a technique for partitioning the edges of the complete graph based on length into a linear number of sets. Among the many different applications of WSPDs, Callahan and Kosaraju proved that the sparse subgraph that results by selecting an arbitrary edge from each set (called WSPDspanner) is a 1 + 8/(s − 4)spanner, where s > 4 is the separation ratio used for partitioning the edges. Although competitive localrouting strategies exist for various spanners such as Yaographs, Θgraphs, and variants of Delaunay graphs, few localrouting strategies are known for any WSPDspanner. Our main contribution is a localrouting algorithm with a nearoptimal competitive routing ratio of 1 + O(1/s) on a WSPDspanner. Specifically, we present a 2local and a 1local routing algorithm on a WSPDspanner with competitive routing ratios of 1+6/(s−2)+4/s and 1+6/(s−2)+ 6/s + 4/(s2 − 2s) + 8/s2respectively.
 Date Created:
 20170101

 Resource Type:
 Conference Proceeding
 Creator:
 Lanthier, Mark, Velazquez, Elio, and Santoro, Nicola
 Abstract:
 This paper proposes a proactive solution to the Frugal Feeding Problem (FFP) in Wireless Sensor Networks. The FFP attempts to find energyefficient routes for a mobile service entity to rendezvous with each member of a team of mobile robots. Although the complexity of the FFP is similar to the Traveling Salesman Problem (TSP), we propose an efficient solution, completely distributed and localized for the case of a fixed rendezvous location (i.e., service facility with limited number of docking ports) and mobile capable entities (sensors). Our proactive solution reduces the FFP to finding energyefficient routes in a dynamic Compass Directed unit Graph (CDG). The proposed CDG incorporates ideas from forward progress routing and the directionality of compass routing in an energyaware unit subgraph. Navigating the CDG guarantees that each sensor will reach the rendezvous location in a finite number of steps. The ultimate goal of our solution is to achieve energy equilibrium (i.e., no further sensor losses due to energy starvation) by optimizing the use of the shared resource (recharge station). We also examine the impact of critical parameters such as transmission range, cost of mobility and sensor knowledge in the overall performance.
 Date Created:
 20111114

 Resource Type:
 Conference Proceeding
 Creator:
 Guo, Yuhong and Li, Xin
 Abstract:
 Multilabel classification is a central problem in many application domains. In this paper, we present a novel supervised bidirectional model that learns a lowdimensional midlevel representation for multilabel classification. Unlike traditional multilabel learning methods which identify intermediate representations from either the input space or the output space but not both, the midlevel representation in our model has two complementary parts that capture intrinsic information of the input data and the output labels respectively under the autoencoder principle while augmenting each other for the target output label prediction. The resulting optimization problem can be solved efficiently using an iterative procedure with alternating steps, while closedform solutions exist for one major step. Our experiments conducted on a variety of multilabel data sets demonstrate the efficacy of the proposed bidirectional representation learning model for multilabel classification.
 Date Created:
 20140101

 Resource Type:
 Conference Proceeding
 Creator:
 White, Anthony and SalehiAbari, Amirali
 Abstract:
 Autonomous agents require trust and reputation concepts in order to identify communities of agents with which to interact reliably in ways analogous to humans. Agent societies are invariably heterogeneous, with multiple decision making policies and actions governing their behaviour. Through the introduction of naive agents, this paper shows empirically that while learning agents can identify malicious agents through direct interaction, naive agents compromise utility through their inability to discern malicious agents. Moreover, the impact of the proportion of naive agents on the society is analyzed. The paper demonstrates that there is a need for witness interaction trust to detect naive agents in addition to the need for direct interaction trust to detect malicious agents. By proposing a set of policies, the paper demonstrates how learning agents can isolate themselves from naive and malicious agents.
 Date Created:
 20100720

 Resource Type:
 Conference Proceeding
 Creator:
 Prencipe, Giuseppe, Cáceres, Edson, Chan, Albert, and Dehne, Frank
 Abstract:
 In this paper, we present parallel algorithms for the coarse grained multicomputer (CGM) and the bulk synchronous parallel computer (BSP) for solving two well known graph problems: (1) determining whether a graph G is bipartite, and (2) determining whether a bipartite graph G is convex. Our algorithms require O(log p) and O(log2 p) communication rounds, respectively, and linear sequential work per round on a CGM with p processors and N/p local memory per processor, N=G. The algorithms assume that N/ p ≥ p€ for some fixed€ > 0, which is true for all commercially available multiprocessors. Our results imply BSP algorithms with O(log p) and O(log2 p) supersteps, respectively, O(g log(p) N p) communication time, and O(log(p) N p) local computation time. Our algorithm for determining whether a bipartite graph is convex includes a novel, coarse grained parallel, version of the PQ tree data structure introduced by Booth and Lueker. Hence, our algorithm also solves, with the same time complexity as indicated above, the problem of testing the consecutiveones property for (0, 1) matrices as well as the chordal graph recognition problem. These, in turn, have numerous applications in graph theory, DNA sequence assembly, database theory, and other areas.
 Date Created:
 20000101

 Resource Type:
 Conference Proceeding
 Creator:
 Maheshwari, Anil and Zeh, Norbert
 Abstract:
 We present external memory algorithms for outerplanarity testing, embedding outerplanar graphs, breadthfirst search (BFS) and depthfirst search (DFS) in outerplanar graphs, and finding a2separator of size 2 for a given outerplanar graph. Our algorithms take O(sort(N)) I/Os and can easily be improved to take O (perm (N)) I/Os, as all these problems have linear time solutions in internal memory. For BFS, DFS, and outerplanar embedding we show matching lower bounds.
 Date Created:
 19990101

 Resource Type:
 Conference Proceeding
 Creator:
 Morin, Pat and Bose, Prosenjit
 Abstract:
 We consider online routing strategies for routing between the vertices of embedded planar straight line graphs. Our results include (1) two deterministic memoryless routing strategies, one that works for all Delaunay triangulations and the other that works for all regular triangulations, (2) a randomized memoryless strategy that works for all triangulations, (3) an O(1) memory strategy that works for all convex subdivisions, (4) an O(1) memory strategy that approximates the shortest path in Delaunay triangulations, and (5) theoretical and experimental results on the competitiveness of these strategies.
 Date Created:
 19990101

 Resource Type:
 Conference Proceeding
 Creator:
 Krizanc, Danny, Kranakis, Evangelos, and Kirousis, Lefteris M.
 Abstract:
 Let φ be a random Boolean formula that is an instance of 3SAT. We consider the problem of computing the least real number such that if the ratio of the number of clauses over the number of variables of φ strictly exceeds κ, then φ is almost certainly unsatisfiable. By a well known and more or less straightforward argument, it can be shown that κ 3.
 Date Created:
 19960101

 Resource Type:
 Conference Proceeding
 Creator:
 Maheshwari, Anil, Sack, JörgRüdiger, Lanthier, Mark, and Aleksandrov, Lyudmil
 Date Created:
 19980101

 Resource Type:
 Conference Proceeding
 Creator:
 Peleg, David, Krizanc, Danny, Kirousis, Lefteris M., Kranakis, Evangelos, Kaklamanis, Christos, and Bose, Prosenjit
 Abstract:
 In wireless communication, the signal of a typical broadcast station is transmited from a broadcast center p and reaches objects at a distance, say, R from it. In addition there is a radius r, r < R, such that the signal originating from the center of the station is so strong that human habitation within distance r from the center p should be avoided. Thus every station determines a region which is an “annulus of permissible habitation". We consider the following station layout (SL) problem: Cover a given (say, rectangular) planar region which includes a collection of orthogonal buildings with a minimum number of stations so that every point in the region is within the reach of a station, while at the same time no building is within the dangerous range of a station. We give algorithms for computing such station layouts in both the oneand twodimensional cases.
 Date Created:
 19990101

 Resource Type:
 Conference Proceeding
 Creator:
 Bose, Prosenjit and Van Renssen, André
 Abstract:
 We present tight upper and lower bounds on the spanning ratio of a large family of constrained θgraphs. We show that constrained θgraphs with 4k2 (k≥ 1 and integer) cones have a tight spanning ratio of 1+2 sin(θ/2), where θ is 2 π/ (4k+2). We also present improved upper bounds on the spanning ratio of the other families of constrained θgraphs.
 Date Created:
 20140101

 Resource Type:
 Conference Proceeding
 Creator:
 Seidel, Raimund, Dehne, Frank, and Klein, Rolf
 Abstract:
 Given a set S of s points in the plane, where do we place a new point, p, in order to maximize the area of its region in the Voronoi diagram of S and p? We study the case where the Voronoi neighbors of p are in convex position, and prove that there is at most one local maximum.
 Date Created:
 20021201

 Resource Type:
 Conference Proceeding
 Creator:
 Mannan, Mohammad, Barrera, David, Van Oorschot, Paul C., Lie, David, and Brown, Carson D.
 Abstract:
 Instead of allowing the recovery of original passwords, forgotten passwords are often reset using online mechanisms such as password verification questions (PVQ methods) and password reset links in email. These mechanisms are generally weak, exploitable, and force users to choose new passwords. Emailing the original password exposes the password to third parties. To address these issues, and to allow forgotten passwords to be securely restored, we present a scheme called Mercury. Its primary mode employs userlevel public keys and a personal mobile device (PMD) such as a smartphone, netbook, or tablet. A user generates a key pair on her PMD; the private key remains on the PMD and the public key is shared with different sites (e.g., during account setup). For password recovery, the site sends the (public key)encrypted password to the user's preregistered email address, or displays the encrypted password on a webpage, e.g., as a barcode. The encrypted password is then decrypted using the PMD and revealed to the user. A prototype implementation of Mercury is available as an Android application.
 Date Created:
 20120221

 Resource Type:
 Conference Proceeding
 Creator:
 Van Walderveen, Freek, Davoodi, Pooya, and Smid, Michiel
 Abstract:
 Given a set of n points in the plane, range diameter queries ask for the furthest pair of points in a given axisparallel rectangular range. We provide evidence for the hardness of designing spaceefficient data structures that support range diameter queries by giving a reduction from the set intersection problem. The difficulty of the latter problem is widely acknowledged and is conjectured to require nearly quadratic space in order to obtain constant query time, which is matched by known data structures for both problems, up to polylogarithmic factors. We strengthen the evidence by giving a lower bound for an important subproblem arising in solutions to the range diameter problem: computing the diameter of two convex polygons, that are separated by a vertical line and are preprocessed independently, requires almost linear time in the number of vertices of the smaller polygon, no matter how much space is used. We also show that range diameter queries can be answered much more efficiently for the case of points in convex position by describing a data structure of size O(n log n) that supports queries in O(log n) time.
 Date Created:
 20120515

 Resource Type:
 Conference Proceeding
 Creator:
 Cervera, Gimer, Barbeau, Michel, GarciaAlfaro, Joaquin, and Kranakis, Evangelos
 Abstract:
 The Hierarchical Optimized Link State Routing (HOLSR) protocol enhances the scalability and heterogeneity of traditional OLSRbased Mobile AdHoc Networks (MANETs). It organizes the network in logical levels and nodes in clusters. In every cluster, it implements the mechanisms and algorithms of the original OLSR to generate and to distribute control traffic information. However, the HOLSR protocol was designed with no security in mind. Indeed, it both inherits, from OLSR, and adds new security threats. For instance, the existence of misbehaving nodes can highly affect important HOLSR operations, such as the cluster formation. Cluster IDentification (CID) messages are implemented to organize a HOLSR network in clusters. In every message, the hop count field indicates to the receiver the distance in hops to the originator. An attacker may maliciously alter the hop count field. As a consequence, a receiver node may join a cluster head farther away than it appears. Then, the scalability properties in a HOLSR network is affected by an unbalanced distribution of nodes per cluster. We present a solution based on the use of hash chains to protect mutable fields in CID messages. As a consequence, when a misbehaving node alters the hop count field in a CID message, the receiver nodes are able of detecting and discarding the invalid message.
 Date Created:
 20120127

 Resource Type:
 Conference Proceeding
 Creator:
 Czyzowicz, Jurek, Opatrny, Jaroslav, Kranakis, Evangelos, Narayanan, Lata, Krizanc, Danny, Stacho, Ladislav, Urrutia, Jorge, Yazdani, Mohammadreza, and Lambadaris, Ioannis
 Abstract:
 A set of sensors establishes barrier coverage of a given line segment if every point of the segment is within the sensing range of a sensor. Given a line segment I, n mobile sensors in arbitrary initial positions on the line (not necessarily inside I) and the sensing ranges of the sensors, we are interested in finding final positions of sensors which establish a barrier coverage of I so that the sum of the distances traveled by all sensors from initial to final positions is minimized. It is shown that the problem is NP complete even to approximate up to constant factor when the sensors may have different sensing ranges. When the sensors have an identical sensing range we give several efficient algorithms to calculate the final destinations so that the sensors either establish a barrier coverage or maximize the coverage of the segment if complete coverage is not feasible while at the same time the sum of the distances traveled by all sensors is minimized. Some open problems are also mentioned.
 Date Created:
 20101213

 Resource Type:
 Conference Proceeding
 Creator:
 Barbeau, Michel, Kranakis, Evangelos, and GarciaAlfaro, Joaquin
 Abstract:
 The design and implementation of security threat mitigation mechanisms in RFID systems, specially in lowcost RFID tags, are gaining great attention in both industry and academia. One main focus of research interests is the authentication and privacy techniques to prevent attacks targeting the insecure wireless channel of these systems. Cryptography is a key tool to address these threats. Nevertheless, strong hardware constraints, such as production costs, power consumption, time of response, and regulations compliance, makes the use of traditional cryptography in these systems a very challenging problem. The use of lowoverhead procedures becomes the main approach to solve these challenging problems where traditional cryptography cannot fit. Recent results and trends, with an emphasis on lightweight techniques for addressing critical threats against lowcost RFID systems, are surveyed.
 Date Created:
 20100503

 Resource Type:
 Conference Proceeding
 Creator:
 Kranakis, Evangelos, Krizanc, Danny, Narayanan, Lata, and Keane, Michael
 Abstract:
 Delay (or disruption) tolerant sensor networks may be modeled as Markovian evolving graphs [1]. We present experimental evidence showing that considering multiple (possibly not shortest) paths instead of one fixed (greedy) path can decrease the expected time to deliver a packet on such a network by as much as 65 per cent depending on the probability that an edge exists in a given time interval. We provide theoretical justification for this result by studying a special case of the Markovian evolving grid graph. We analyze a natural algorithm for routing on such networks and show that it is possible to improve the expected time of delivery by up to a factor of two depending upon the probability of an edge being up during a time step and the relative positions of the source and destination. Furthermore we show that this is optimal, i.e., no other algorithm can achieve a better expected running time. As an aside, our results give high probability bounds for Knuth's toilet paper problem [11].
 Date Created:
 20091201

 Resource Type:
 Conference Proceeding
 Creator:
 He, Meng, Dillabaugh, Craig, Zeh, Norbert, and Maheshwari, Anil
 Date Created:
 20091201

 Resource Type:
 Conference Proceeding
 Creator:
 Krizanc, D., Yazdani, M., Stacho, L., Narayanan, L., Lambadaris, Ioannis, Opatrny, J., Czyzowicz, J., Kranakis, Evangelos, and Urrutia, J.
 Abstract:
 We consider n mobile sensors located on a line containing a barrier represented by a finite line segment. Sensors form a wireless sensor network and are able to move within the line. An intruder traversing the barrier can be detected only when it is within the sensing range of at least one sensor. The sensor network establishes barrier coverage of the segment if no intruder can penetrate the barrier from any direction in the plane without being detected. Starting from arbitrary initial positions of sensors on the line we are interested in finding final positions of sensors that establish barrier coverage and minimize the maximum distance traversed by any sensor. We distinguish several variants of the problem, based on (a) whether or not the sensors have identical ranges, (b) whether or not complete coverage is possible and (c) in the case when complete coverage is impossible, whether or not the maximal coverage is required to be contiguous. For the case of n sensors with identical range, when complete coverage is impossible, we give linear time optimal algorithms that achieve maximal coverage, both for the contiguous and noncontiguous case. When complete coverage is possible, we give an O(n 2) algorithm for an optimal solution, a linear time approximation scheme with approximation factor 2, and a (1∈+∈ε) PTAS. When the sensors have unequal ranges we show that a variation of the problem is NPcomplete and identify some instances which can be solved with our algorithms for sensors with unequal ranges.
 Date Created:
 20091019

 Resource Type:
 Conference Proceeding
 Creator:
 Barbeau, Michel and Laurendeau, Christine
 Abstract:
 Increasingly ubiquitous wireless technologies require novel localization techniques to pinpoint the position of an uncooperative node, whether the target be a malicious device engaging in a security exploit or a lowbattery handset in the middle of a critical emergency. Such scenarios necessitate that a radio signal source be localized by other network nodes efficiently, using minimal information. We propose two new algorithms for estimating the position of an uncooperative transmitter, based on the received signal strength (RSS) of a single target message at a set of receivers whose coordinates are known. As an extension to the concept of centroid localization, our mechanisms weigh each receiver's coordinates based on the message's relative RSS at that receiver, with respect to the span of RSS values over all receivers. The weights may decrease from the highest RSS receiver either linearly or exponentially. Our simulation results demonstrate that for all but the most sparsely populated wireless networks, our exponentially weighted mechanism localizes a target node within the regulations stipulated for emergency services location accuracy.
 Date Created:
 20090928

 Resource Type:
 Conference Proceeding
 Creator:
 Dillabaugh, Craig, He, Meng, and Maheshwari, Anil
 Abstract:
 We present two results for path traversal in trees, where the traversal is performed in an asymptotically optimal number of I/Os and the tree structure is represented succinctly. Our first result is for bottomup traversal that starts with a node in the tree T and traverses a path to the root. For blocks of size B, a tree on N nodes, and for a path of length K, we design data structures that permit traversal of the bottomup path in O(K/B) I/Os using only bits, for an arbitrarily selected constant, ε, where 0∈<∈ε<∈1. Our second result is for topdown traversal in binary trees. We store T using (3∈+∈q)N∈+∈o(N) bits, where q is the number of bits required to store a key, while topdown traversal can still be performed in an asymptotically optimal number of I/Os.
 Date Created:
 20081201

 Resource Type:
 Conference Proceeding
 Creator:
 Petriu, Dorina C. and Tawhid, Rasha
 Abstract:
 The paper proposes to integrate performance analysis in the early phases of the modeldriven development process for Software Product Lines (SPL). We start by adding generic performance annotations to the UML model representing the set of core reusable SPL assets. The annotations are generic and use the MARTE Profile recently adopted by OMG. A first model transformation realized in the Atlas Transformation Language (ATL), which is the focus of this paper, derives the UML model of a specific product with concrete MARTE performance annotations from the SPL model. A second transformation generates a Layered Queueing Network performance model for the given product by applying an existing transformation approach named PUMA, developed in previous work. The proposed technique is illustrated with an ecommerce case study that models the commonality and variability in both structural and behavioural SPL views. A product is derived and the performance of two design alternatives is compared.
 Date Created:
 20081128

 Resource Type:
 Conference Proceeding
 Creator:
 Kranakis, Evangelos and Wiese, Andreas
 Abstract:
 We investigate the problem of locally coloring and constructing special spanners of location aware Unit Disk Graphs (UDGs). First we present a local approximation algorithm for the vertex coloring problem in UDGs which uses at most four times as many colors as required by an optimal solution. Then we look at the colorability of spanners of UDGs. In particular we present a local algorithm for constructing a 4colorable spanner of a unit disk graph. The output consists of the spanner and the 4coloring. The computed spanner also has the properties that it is planar, the degree of a vertex in the spanner is at most 5 and the angles between two edges are at least π/3. By enlarging the locality distance (i.e. the size of the neighborhood which a vertex has to explore in order to compute its color) we can ensure the total weight of the spanner to be arbitrarily close to the weight of a minimum spanning tree. We prove that a local algorithm cannot compute a bipartite spanner of a unit disk graph and therefore our algorithm needs at most one color more than any local algorithm for the task requires. Moreover, we prove that there is no local algorithm for 3coloring UDGs or spanners of UDGs, even if the 3colorability of the graph (or the spanner respectively) is guaranteed in advance.
 Date Created:
 20081201

 Resource Type:
 Conference Proceeding
 Creator:
 Bose, Prosenjit, Maheshwari, Anil, Carmi, Paz, Smid, Michiel, and Farshi, Mohammad
 Abstract:
 It is wellknown that the greedy algorithm produces high quality spanners and therefore is used in several applications. However, for points in ddimensional Euclidean space, the greedy algorithm has cubic running time. In this paper we present an algorithm that computes the greedy spanner (spanner computed by the greedy algorithm) for a set of n points from a metric space with bounded doubling dimension in time using space. Since the lower bound for computing such spanners is Ω(n 2), the time complexity of our algorithm is optimal to within a logarithmic factor.
 Date Created:
 20081027

 Resource Type:
 Conference Proceeding
 Creator:
 Kranakis, Evangelos, Shi, Q., Bhattacharya, B., Wiese, A., Burmester, B., and Hu, Y.
 Abstract:
 Intrusion detection, area coverage and border surveillance are important applications of wireless sensor networks today. They can be (and are being) used to monitor large unprotected areas so as to detect intruders as they cross a border or as they penetrate a protected area. We consider the problem of how to optimally move mobile sensors to the fence (perimeter) of a region delimited by a simple polygon in order to detect intruders from either entering its interior or exiting from it. We discuss several related issues and problems, propose two models, provide algorithms and analyze their optimal mobility behavior.
 Date Created:
 20080922

 Resource Type:
 Conference Proceeding
 Creator:
 Couture, Mathieu, Smid, Michiel, Maheshwari, Anil, Bose, Prosenjit, Carmi, Paz, and Zeh, Norbert
 Abstract:
 Given an integer k ≥ 2, we consider the problem of computing the smallest real number t(k) such that for each set P of points in the plane, there exists a t(k)spanner for P that has chromatic number at most k. We prove that t(2)∈=∈3, t(3)∈=∈2, , and give upper and lower bounds on t(k) for k∈>∈4. We also show that for any ε>∈0, there exists a (1∈+∈ε)t(k)spanner for P that has O(P) edges and chromatic number at most k. Finally, we consider an online variant of the problem where the points of P are given one after another, and the color of a point must be assigned at the moment the point is given. In this setting, we prove that t(2)∈=∈3, , , and give upper and lower bounds on t(k) for k∈>∈4.
 Date Created:
 20080827

 Resource Type:
 Conference Proceeding
 Creator:
 Kranakis, Evangelos and Wiese, Andreas
 Abstract:
 We present the first local approximation schemes for maximum independent set and minimum vertex cover in unit disk graphs. In the graph model we assume that each node knows its geographic coordinates in the plane (location aware nodes). Our algorithms are local in the sense that the status of each node v (whether or not v is in the computed set) depends only on the vertices which are a constant number of hops away from v. This constant is independent of the size of the network. We give upper bounds for the constant depending on the desired approximation ratio. We show that the processing time which is necessary in order to compute the status of a single vertex is bounded by a polynomial in the number of vertices which are at most a constant number of vertices away from it. Our algorithms give the best possible approximation ratios for this setting. The technique which we use to obtain the algorithm for vertex cover can also be employed for constructing the first global PTAS for this problem in unit disk graph which does not need the embedding of the graph as part of the input.
 Date Created:
 20080701

 Resource Type:
 Conference Proceeding
 Creator:
 Biddle, Robert, Noble, James, Barr, Pippin, Fischer, Ronald, and Khaled, Rilla
 Abstract:
 Persuasive technologies are increasingly ubiquitous, but the strategies they utilise largely originate in America. Consumer behaviour research shows us that certain persuasion strategies will be more effective on some cultures than others. We claim that the existing strategies will be less effective on nonAmerican audiences than they are on American audiences, and we use information from interviews to show that there exists much scope to develop persuasive technologies from a collectivismfocused perspective. To illustrate the development of such a tool, we describe the design of a collectivismfocused financial planning tool.
 Date Created:
 20060717

 Resource Type:
 Conference Proceeding
 Creator:
 Smid, Michiel and Gudmundsson, Joachim
 Abstract:
 Given a connected geometric graph G, we consider the problem of constructing a tspanner of G having the minimum number of edges. We prove that for every t with 1 1+1/t) edges. This bound almost matches the known upper bound, which states that every connected weighted graph with n vertices contains a tspanner with O(tn1+2/(t+1)) edges. We also prove that the problem of deciding whether a given geometric graph contains a tspanner with at most K edges is NPhard. Previously, this NPhardness result was only known for nongeometric graphs.
 Date Created:
 20060101

 Resource Type:
 Conference Proceeding
 Creator:
 Mirandola, Raffaela, Grassi, Vincenzo, Sabetta, Antonino, and Petriu, Dorina C.
 Abstract:
 The verification of nonfunctional requirements of software models (such as performance, reliability, scalability, security, etc.) requires the transformation of UML models into different analysis models such as Petri nets, queueing networks, formal logic, etc., which represent the system at a higher level of abstraction. The paper proposes a new "abstractionraising" transformation approach for generating analysis models from UML models. In general, such transformations must bridge a large semantic gap between the source and the target model. The proposed approach is illustrated by a transformation from UML to Klaper (Kernel LAnguage for PErformance and Reliability analysis of componentbased systems).
 Date Created:
 20060706

 Resource Type:
 Conference Proceeding
 Creator:
 Dujmović, Vida, Wood, David, and Bose, Prosenjit
 Abstract:
 We prove that for all 0 ≤ t ≤ k and d ≥ 2k, every graph G with treewidth at most k has a 'large' induced subgraph H, where H has treewidth at most t and every vertex in H has degree at most d in G, The order of H depends on t, k, d, and the order of G. With t = k, we obtain large sets of bounded degree vertices. With t = 0, we obtain large independent sets of bounded degree. In both these cases, our bounds on the order of H are tight. For bounded degree independent sets in trees, we characterise the extremal graphs. Finally, we prove that an interval graph with maximum clique size k has a maximum independent set in which every vertex has degree at most 2k.
 Date Created:
 20051201

 Resource Type:
 Conference Proceeding
 Creator:
 Kranakis, Evangelos, Morin, Pat, and Krizanc, Danny
 Abstract:
 We present a tradeoff between the expected time for two identical agents to rendezvous on a synchronous, anonymous, oriented ring and the memory requirements of the agents. In particular, we show that there exists a 2t state agent, which can achieve rendezvous on an n node ring in expected time O( n 2/2 t ∈+∈2 t ) and that any t/2 state agent requires expected time Ω( n 2/2 t ). As a corollary we observe that Θ(loglogn) bits of memory are necessary and sufficient to achieve rendezvous in linear time.
 Date Created:
 20080512

 Resource Type:
 Conference Proceeding
 Creator:
 Markou, Euripides, Kranakis, Evangelos, and Krizanc, Danny
 Abstract:
 We consider the rendezvous problem for identical mobile agents (i.e., running the same deterministic algorithm) with tokens in a synchronous torus with a sense of direction and show that there is a striking computational difference between one and more tokens. More specifically, we show that 1) two agents with a constant number of unmovable tokens, or with one movable token, each cannot rendezvous if they have o(log n) memory, while they can perform rendezvous with detection as long as they have one unmovable token and O(log n) memory; in contrast, 2) when two agents have two movable tokens each then rendezvous (respectively, rendezvous with detection) is possible with constant memory in an arbitrary n × m (respectively, n × n) torus; and finally, 3) two agents with three movable tokens each and constant memory can perform rendezvous with detection in a n × m torus. This is the first publication in the literature that studies tradeoffs between the number of tokens, memory and knowledge the agents need in order to meet in such a network.
 Date Created:
 20060710

 Resource Type:
 Conference Proceeding
 Creator:
 Loke, R. K.S. and Oommen, B. John
 Abstract:
 We consider a problem which can greatly enhance the areas of cursive script recognition and the recognition of printed character sequences. This problem involves recognizing words/strings by processing their noisy subsequences. Let X* be any unknown word from a finite dictionary H. Let U be any arbitrary subsequence of X*. We study the problem of estimating X* by processing Y, a noisy version of U. Y contains substitution, insertion, deletion and generalized transposition errors — the latter occurring when transposed characters are themselves subsequently substituted. We solve the noisy subsequence recognition problem by defining and using the constrained edit distance between X ε H and Y subject to any arbitrary edit constraint involving the number and type of edit operations to be performed. An algorithm to compute this constrained edit distance has been presented. Using these algorithms we present a syntactic Pattern Recognition (PR) scheme which corrects noisy text containing all these types of errors. Experimental results which involve strings of lengths between 40 and 80 with an average of 30.24 deleted characters and an overall average noise of 68.69 % demonstrate the superiority of our system over existing methods.
 Date Created:
 19950101

 Resource Type:
 Conference Proceeding
 Creator:
 Jiang, Lei, Bertossi, Leopoldo, and Rizzolo, Flavio
 Abstract:
 We motivate, formalize and investigate the notions of data quality assessment and data quality query answering as context dependent activities. Contexts for the assessment and usage of a data source at hand are modeled as collections of external databases, that can be materialized or virtual, and mappings within the collections and with the data source at hand. In this way, the context becomes "the complement" of the data source wrt a data integration system. The proposed model allows for natural extensions, like considering data quality predicates, and even more expressive ontologies for data quality assessment.
 Date Created:
 20110101

 Resource Type:
 Conference Proceeding
 Creator:
 Smid, Michiel
 Date Created:
 20091016

 Resource Type:
 Conference Proceeding
 Creator:
 Ponce, Oscar Morales, Pacheco, Eduardo, Kranakis, Evangelos, Ga̧sieniec, Leszek, Czyzowicz, Jurek, and Kosowski, Adrian
 Abstract:
 A collection of n anonymous mobile robots is deployed on a unitperimeter ring or a unitlength line segment. Every robot starts moving at constant speed, and bounces each time it meets any other robot or segment endpoint, changing its walk direction. We study the problem of position discovery, in which the task of each robot is to detect the presence and the initial positions of all other robots. The robots cannot communicate or perceive information about the environment in any way other than by bouncing. Each robot has a clock allowing it to observe the times of its bounces. The robots have no control on their walks, which are determined by their initial positions and the starting directions. Each robot executes the same position detection algorithm, which receives input data in realtime about the times of the bounces, and terminates when the robot is assured about the existence and the positions of all the robots. Some initial configuration of robots are shown to be infeasible  no position detection algorithm exists for them. We give complete characterizations of all infeasible initial configurations for both the ring and the segment, and we design optimal position detection algorithms for all feasible configurations. For the case of the ring, we show that all robot configurations in which not all the robots have the same initial direction are feasible. We give a position detection algorithm working for all feasible configurations. The cost of our algorithm depends on the number of robots starting their movement in each direction. If the less frequently used initial direction is given to k ≤ n/2 robots, the time until completion of the algorithm by the last robot is 1/2 ⌈n/k⌉. We prove that this time is optimal. By contrast to the case of the ring, for the unit segment we show that the family of infeasible configurations is exactly the set of socalled symmetric configurations. We give a position detection algorithm which works for all feasible configurations on the segment in time 2, and this algorithm is also proven to be optimal.
 Date Created:
 20121109

 Resource Type:
 Conference Proceeding
 Creator:
 Gardezi, Jaffer and Bertossi, Leopoldo
 Abstract:
 Matching Dependencies (MDs) are a recent proposal for declarative entity resolution. They are rules that specify, given the similarities satisfied by values in a database, what values should be considered duplicates, and have to be matched. On the basis of a chaselike procedure for MD enforcement, we can obtain clean (duplicatefree) instances; actually possibly several of them. The clean answers to queries (which we call the resolved answers) are invariant under the resulting class of instances. In this paper, we investigate a query rewriting approach to obtaining the resolved answers (for certain classes of queries and MDs). The rewritten queries are specified in stratified Datalog not,s with aggregation. In addition to the rewriting algorithm, we discuss the semantics of the rewritten queries, and how they could be implemented by means of a DBMS.
 Date Created:
 20121010

 Resource Type:
 Conference Proceeding
 Creator:
 Smid, Michiel, Maheshwari, Anil, Das, Sandip, and Banik, Aritra
 Abstract:
 Let P be a simple polygon with m vertices and let be a set of n points in P. We consider the points of to be users. We consider a game with two players and. In this game, places a point facility inside P, after which places another point facility inside P. We say that a user is served by its nearest facility, where distances are measured by the geodesic distance in P. The objective of each player is to maximize the number of users they serve. We show that for any given placement of a facility by, an optimal placement for can be computed in O(m + n(logn + logm)) time. We also provide a polynomialtime algorithm for computing an optimal placement for.
 Date Created:
 20131008

 Resource Type:
 Conference Proceeding
 Creator:
 Zeh, Norbert, Hutchinson, David, and Maheshwari, Anil
 Abstract:
 We present results related to satisfying shortest path queries on a planar graph stored in external memory. In particular, we show how to store rooted trees in external memory so that bottomup paths can be traversed I/Oefficiently, and we present I/Oefficient algorithms for triangulating planar graphs and computing small separators of such graphs. Using these techniques, we can construct a data structure that allows for answering shortest path queries on a planar graph I/Oefficiently.
 Date Created:
 19990101

 Resource Type:
 Conference Proceeding
 Creator:
 Bose, Prosenjit, Howat, John, and Morin, Pat
 Abstract:
 The time required for a sequence of operations on a data structure is usually measured in terms of the worst possible such sequence. This, however, is often an overestimate of the actual time required. Distributionsensitive data structures attempt to take advantage of underlying patterns in a sequence of operations in order to reduce time complexity, since access patterns are nonrandom in many applications. Unfortunately, many of the distribution sensitive structures in the literature require a great deal of space overhead in the form of pointers. We present a dictionary data structure that makes use of both randomization and existing spaceefficient data structures to yield very low space overhead while maintaining distribution sensitivity in the expected sense.
 Date Created:
 20090914

 Resource Type:
 Conference Proceeding
 Creator:
 Smid, Michiel, Zeh, Norbert, and Maheshwari, Anil
 Abstract:
 We present I/Oefficient algorithms to construct planar Steiner spanners for point sets and sets of polygonal obstacles in the plane, and for constructing the “dumbbell” spanner of [6] for point sets in higher dimensions. As important ingredients to our algorithms, we present I/O efficient algorithms to color the vertices of a graph of bounded degree, answer binary search queries on topology buffer trees, and preprocess a rooted tree for answering prioritized ancestor queries.
 Date Created:
 20010101

 Resource Type:
 Conference Proceeding
 Creator:
 Bose, Prosenjit, Maheshwari, Anil, He, Meng, and Morin, Pat
 Abstract:
 We present a succinct representation of a set of n points on an n×n grid using bits to support orthogonal range counting in time, and range reporting in time, where k is the size of the output. This achieves an improvement on query time by a factor of upon the previous result of Mäkinen and Navarro [1], while using essentially the informationtheoretic minimum space. Our data structure not only can be used as a key component in solutions to the general orthogonal range search problem to save storage cost, but also has applications in text indexing. In particular, we apply it to improve two previous spaceefficient text indexes that support substring search [2] and positionrestricted substring search [1]. We also use it to extend previous results on succinct representations of sequences of small integers, and to design succinct data structures supporting certain types of orthogonal range query in the plane.
 Date Created:
 20090914

 Resource Type:
 Conference Proceeding
 Creator:
 Farshi, Mohammad, Abam, Mohammad Ali, Smid, Michiel, and Carmi, Paz
 Abstract:
 A SemiSeparated Pair Decomposition (SSPD), with parameter s > 1, of a set is a set {(A i ,B i )} of pairs of subsets of S such that for each i, there are balls and containing A i and B i respectively such that min ( radius ) , radius ), and for any two points p, q S there is a unique index i such that p A i and q B i or viceversa. In this paper, we use the SSPD to obtain the following results: First, we consider the construction of geometric tspanners in the context of imprecise points and we prove that any set of n imprecise points, modeled as pairwise disjoint balls, admits a tspanner with edges which can be computed in time. If all balls have the same radius, the number of edges reduces to . Secondly, for a set of n points in the plane, we design a query data structure for halfplane closestpair queries that can be built in time using space and answers a query in time, for any ε> 0. By reducing the preprocessing time to and using space, the query can be answered in time. Moreover, we improve the preprocessing time of an existing axisparallel rectangle closestpair query data structure from quadratic to nearlinear. Finally, we revisit some previously studied problems, namely spanners for complete kpartite graphs and lowdiameter spanners, and show how to use the SSPD to obtain simple algorithms for these problems.
 Date Created:
 20090914

 Resource Type:
 Conference Proceeding
 Creator:
 Smid, Michiel and Gudmundsson, Joachim
 Date Created:
 20130924

 Resource Type:
 Conference Proceeding
 Creator:
 Shi, Wei, Santoro, Nicola, Královič, R., and Dobrev, S.
 Abstract:
 A black hole is a highly harmful host that disposes of visiting agents upon their arrival. It is known that it is possible for a team of mobile agents to locate a black hole in an asynchronous ring network if each node is equipped with a whiteboard of at least O(log n) dedicated bits of storage. In this paper, we consider the less powerful token model: each agent has has available a bounded number of tokens that can be carried, placed on a node or removed from it. All tokens are identical (i.e., indistinguishable) and no other form of communication or coordination is available to the agents. We first of all prove that a team of two agents is sufficient to locate the black hole in finite time even in this weaker coordination model. Furthermore, we prove that this can be accomplished using only O(nlogn) moves in total, which is optimal, the same as with whiteboards. Finally, we show that to achieve this result the agents need to use only O(1) tokens each.
 Date Created:
 20060101

 Resource Type:
 Conference Proceeding
 Creator:
 Gudmundsson, Joachim, Farshi, Mohammad, Smid, Michiel, De Berg, Mark, and Ali Abam, Mohammad
 Abstract:
 Let (S,d) be a finite metric space, where each element p S has a nonnegative weight w(p). We study spanners for the set S with respect to weighted distance function d w , where d w (p,q) is w(p)+d(p,q)+wq if p≠q and 0 otherwise. We present a general method for turning spanners with respect to the dmetric into spanners with respect to the d w metric. For any given ε>0, we can apply our method to obtain (5+ε)spanners with a linear number of edges for three cases: points in Euclidean space ℝ d , points in spaces of bounded doubling dimension, and points on the boundary of a convex body in ℝ d where d is the geodesic distance function. We also describe an alternative method that leads to (2+ε)spanners for points in ℝ d and for points on the boundary of a convex body in ℝ d . The number of edges in these spanners is O(nlogn). This bound on the stretch factor is nearly optimal: in any finite metric space and for any ε>0, it is possible to assign weights to the elements such that any noncomplete graph has stretch factor larger than 2ε.
 Date Created:
 20091102

 Resource Type:
 Conference Proceeding
 Creator:
 Guo, Yuhong
 Abstract:
 In this paper, we present a novel semidefinite programming approach for multipleinstance learning. We first formulate the multipleinstance learning as a combinatorial maximum margin optimization problem with additional instance selection constraints within the framework of support vector machines. Although solving this primal problem requires nonconvex programming, we nevertheless can then derive an equivalent dual formulation that can be relaxed into a novel convex semidefinite programming (SDP). The relaxed SDP has free parameters where T is the number of instances, and can be solved using a standard interiorpoint method. Empirical study shows promising performance of the proposed SDP in comparison with the support vector machine approaches with heuristic optimization procedures.
 Date Created:
 20091201

 Resource Type:
 Conference Proceeding
 Creator:
 Wiese, Andreas and Kranakis, Evangelos
 Date Created:
 20081126

 Resource Type:
 Conference Proceeding
 Creator:
 Kranakis, Evangelos, Pelc, Andrzej, and Paquette, Michel
 Abstract:
 We study the feasibility and time of communication in random geometric radio networks, where nodes fail randomly with positive correlation. We consider a set of radio stations with the same communication range, distributed in a random uniform way on a unit square region. In order to capture fault dependencies, we introduce the ranged spot model in which damaging events, called spots, occur randomly and independently on the region, causing faults in all nodes located within distance s from them. Node faults within distance 2s become dependent in this model and are positively correlated. We investigate the impact of the spot arrival rate on the feasibility and the time of communication in the faultfree part of the network. We provide an algorithm which broadcasts correctly with probability 1  ε in faulty random geometric radio networks of diameter D in time O(D + log1/ε).
 Date Created:
 20081126

 Resource Type:
 Conference Proceeding
 Creator:
 Whitehead, Anthony D.
 Abstract:
 we present a method of segmenting video to detect cuts with accuracy equal to or better than both histogram and other feature based methods. As well, the method is faster than other feature based methods. By utilizing feature tracking on corners, rather than lines, we are able to reliably detect features such as cuts, fades and salient frames. Experimental evidence shows that the method is able to withstand high motion situations better than existing methods. Initial implementations using full sized video frames are able to achieve processing rates of 1030 frames per second depending on the level of motion and number of features being tracked; this includes the time to generate the MPEG decompressed frames.
 Date Created:
 20030101

 Resource Type:
 Conference Proceeding
 Creator:
 Nayak, Amiya, Du, Jingzhe, and Kranakis, Evangelos
 Abstract:
 We describe a novel Distributed Storage protocol in Disruption (Delay) Tolerant Networks (DTN). Since DTNs can not guarantee the connectivity of the network all the time, distributed data storage and look up has to be performed in a storeandforward way. In this work, we define local distributed location regions which are called cells to facilitate the data storage and look up process. Nodes in a cell have high probability of moving within their cells. Our protocol resorts to storing data items in cells which have hierarchical structure to reduce routing information storage at nodes. Multiple copies of a data item may be stored at nodes to counter the adverse impact of the nature of DTNs. The cells are relatively stable regions and as a result, data exchange overheads among nodes are reduced. Through experimentation, we show that the proposed distributed storage protocol achieves higher successful data storage ratios with lower delays and limited data item exchange requirements than other protocols in the literature.
 Date Created:
 20100827

 Resource Type:
 Conference Proceeding
 Creator:
 Yanikomeroglu, Halim and AlAhmadi, Saad
 Date Created:
 20091019

 Resource Type:
 Conference Proceeding
 Creator:
 Noble, James, Marshall, Stuart, Anslow, Craig, and Biddle, Robert
 Abstract:
 Developing applications for touch devices is hard. Developing touch based applications for multiuser input is harder. The MultiTouch for Java (MT4j) toolkit supports developing touch based applications for multiple users. In this paper, we outline our experience using MT4j for developing a number of software applications to support developers working in colocated teams. Our experience using the toolkit will help developers to understand the nuances of the toolkit and design issues that can be applied to other toolkits for developing multiuser touch based applications.
 Date Created:
 20161021

 Resource Type:
 Conference Proceeding
 Creator:
 Brubaker, Jed R., Handel, Mark, Yarosh, Svetlana, Bivens, Rena, Haimson, Oliver L., and Lingel, Jessa
 Abstract:
 Online systems often struggle to account for the complicated selfpresentation and disclosure needs of those with complex identities or specialized anonymity. Using the lenses of gender, recovery, and performance, our proposed panel explores the tensions that emerge when the richness and complexity of individual personalities and subjectivities run up against design norms that imagine identity as simplistic or onedimensional. These models of identity not only limit the ways individuals can express their own identities, but also establish norms for other users about what to expect, causing further issues when the inevitable dislocations do occur. We discuss the challenges in translating identity into these systems, and how this is further marred by technical requirements and normative logics that structure cultures and practices of databases, algorithms and computer programming.
 Date Created:
 20150101

 Resource Type:
 Conference Proceeding
 Creator:
 Foster, Blair and Somayaji, Anil
 Abstract:
 This paper presents ObjRecombGA, a genetic algorithm framework for recombining related programs at the object file level. A genetic algorithm guides the selection of object files, while a robust link resolver allows working program binaries to be produced from the object files derived from two ancestor programs. Tests on compiled C programs, including a simple web browser and a wellknown 3D video game, show that functional program variants can be created that exhibit key features of both ancestor programs. This work illustrates the feasibility of applying evolutionary techniques directly to commodity applications. Copyright 2010 ACM.
 Date Created:
 20100827

 Resource Type:
 Conference Proceeding
 Creator:
 Van Oorschot, Paul C., Biddle, Robert, Forget, Alain, Chiasson, Sonia, and Stobert, Elizabeth
 Abstract:
 The underlying issues relating to the usability and security of multiple passwords are largely unexplored. However, we know that people generally have difficulty remembering multiple passwords. This reduces security since users reuse the same password for different systems or reveal other passwords as they try to log in. We report on a laboratory study comparing recall of multiple text passwords with recall of multiple clickbased graphical passwords. In a onehour session (shortterm), we found that participants in the graphical password condition coped significantly better than those in the text password condition. In particular, they made fewer errors when recalling their passwords, did not resort to creating passwords directly related to account names, and did not use similar passwords across multiple accounts. After two weeks, participants in the two conditions had recall success rates that were not statistically different from each other, but those with text passwords made more recall errors than participants with graphical passwords. In our study, clickbased graphical passwords were significantly less susceptible to multiple password interference in the shortterm, while having comparable usability to text passwords in most other respects. Copyright 2009 ACM.
 Date Created:
 20091201

 Resource Type:
 Conference Proceeding
 Creator:
 Neely, Colleen, Davis, Kate, Jin, Lei, and Rykse, Harriet
 Abstract:
 Presented at Electronic Resources & Libraries Conference, Austin, TX, February 28, 2011.
 Date Created:
 20110228

 Resource Type:
 Conference Proceeding
 Creator:
 Hilton, Robert, Stoney, Christopher, and Shepherd, Robert
 Date Created:
 20100601

 Resource Type:
 Conference Proceeding
 Creator:
 Walsh, John C.
 Date Created:
 20110531

 Resource Type:
 Conference Proceeding
 Creator:
 Chiasson, Sonia, Forget, Alain, Biddle, Robert, and Van Oorschot, Paul C.
 Abstract:
 Usable security has unique usability challenges because the need for security often means that standard humancomputerinteraction approaches cannot be directly applied. An important usability goal for authentication systems is to support users in selecting better passwords, thus increasing security by expanding the effective password space. In clickbased graphical passwords, poorly chosen passwords lead to the emergence of hotspots ' portions of the image where users are more likely to select clickpoints, allowing attackers to mount more successful dictionary attacks. We use persuasion to influence user choice in clickbased graphical passwords, encouraging users to select more random, and hence more secure, clickpoints. Our approach is to introduce persuasion to the Cued ClickPoints graphical password scheme (Chiasson, van Oorschot, Biddle, 2007). Our resulting scheme significantly reduces hotspots while still maintaining its usability.
 Date Created:
 20080101

 Resource Type:
 Conference Proceeding
 Creator:
 Bucking, Scott, Zmeureanu, Radu, and Athienitis, Andreas
 Abstract:
 This paper presents a multiobjective redesign case study of an archetype solar house based on a near net zero energy (NZE) demonstration home located in Eastman, Quebec. Using optimization techniques, pathways are identified from the original design to both cost and energy optimal designs. An evolutionary algorithm is used to optimize tradeoffs between passive solar gains and active solar generation, using two objective functions: netenergy consumption and lifecycle cost over a thirtyyear life cycle. In addition, this paper explores different pathways to net zero energy based on economic incentives, such as feedin tariffs for onsite electricity production from renewables. The main objective is to identify pathways to net zero energy that will facilitate the future systematic design of similar homes based on the concept of the archetype that combines passive solar design; energyefficiency measures, including a geothermal heat pump; and a buildingintegrated photovoltaic system. Results from this paper can be utilized as follows: (1) systematic design improvements and applications of lessons learned from a proven NZE home design concept, (2) use of a methodology to understand pathways to cost and energy optimal building designs, and (3) to aid in policy development on economic incentives that can positively influence optimized home design.
 Date Created:
 20140101

 Resource Type:
 Conference Proceeding
 Creator:
 Opp, James and Whitehead, Anthony D.
 Abstract:
 In this work we discuss our efforts to use the ubiquity of smart phone systems and the mobility they provide to stream historical information about your current place on the earth to the end user. We propose the concept of timescapes to portray this historical significance of where they are standing and allow a brief travel through time. By combining GPS location, with a rich media interpretation of existing historical documents, historical facts become an ondemand resource available to travellers, school children, historians and any interested 3rd party. To our knowledge this is the first introduction of the term timescape to be used in the context of historical information pull. Copyright
 Date Created:
 20130905

 Resource Type:
 Conference Proceeding
 Creator:
 Whitehead, Anthony D.
 Abstract:
 There have been a number of steganography embedding techniques proposed over the past few years. In turn, there has been great interest in steganalysis techniques as the embedding techniques improve. Specifically, universal steganalysis techniques have become more attractive since they work independently of the embedding technique. In this work, we examine the effectiveness of a basic universal technique that relies on some knowledge about the cover media, but not the embedding technique. We consider images as a cover media, and examine how a single technique that we call steganographic sanitization performs on 26 different steganography programs that are publicly available on the Internet. Our experiments are completed using a number of secret messages and a variety of different levels of sanitization. However, since our intent is to remove covert communication, and not authentication information, we examine how well the sanitization process preserves authentication information such as watermarks and digital fingerprints.
 Date Created:
 20051201

 Resource Type:
 Conference Proceeding
 Creator:
 Neely, Colleen
 Abstract:
 Webinar presented to members of the Ontario Council of University Libraries, June 29, 2011.
 Date Created:
 20110629

 Resource Type:
 Conference Proceeding
 Creator:
 Cross, Emma
 Date Created:
 20170531

 Resource Type:
 Conference Proceeding
 Creator:
 Cross, Emma and Merriam, Helena
 Date Created:
 20170512

 Resource Type:
 Conference Proceeding
 Creator:
 Cross, Emma
 Abstract:
 Resource Description and Access is the new content standard coming Spring 2013, with national libraries using RDA effective March 30, 2013. Libraries need to address training for staff in all departments on how to interpret, catalogue and use RDA records.
 Date Created:
 20130213

 Resource Type:
 Conference Proceeding
 Creator:
 Duimovich, George
 Abstract:
 Presentation to Data Science Seminar at Carleton University, Institute for Data Science, May 11, 2016.
 Date Created:
 20160511

 Resource Type:
 Conference Proceeding
 Creator:
 Bucking, Scott
 Abstract:
 Netzero energy is an influential idea in guiding the building stock towards renewable energy resources. Increasingly, this target is scaled to entire communities which may include dozens of buildings in each new development phase. Although building energy modelling processes and codes have been well developed to guide decision making, there is a lack of methodologies for community integrated energy masterplanning. The problem is further complicated by the availability of district systems which better harvest and store onsite renewable energy. In response to these challenges, this paper contributes an energy modelling methodology which helps energy masterplanners determine tradeoffs between building energy saving measures and district system design. Furthermore, this paper shows that it is possible to mitigate electrical and thermal peaks of a netzero energy community using minimal district equipment. The methodology is demonstrated using a coldclimate casestudy with both significant heating/ cooling loads and solar energy resources.
 Date Created:
 20170725

 Resource Type:
 Conference Proceeding
 Creator:
 Tudin, Susan
 Abstract:
 Poster presented at the Teaching & Learning Symposium, Carleton University, May 11, 2016
 Date Created:
 20160511

 Resource Type:
 Conference Proceeding
 Creator:
 Tucci, Ryan
 Abstract:
 Libraries are quickly becoming spaces for more than just books and journals. At Carleton University MacOdrum Library, we used Minecraft to introduce elementary and high school students to the power of gaming as a tool to foster education, research and collaboration. In May 2015, we encouraged students to take part in a project that engaged them with a local project called the LeBreton Flats Redevelopment Project. The redevelopment project led by the National Capital Commission (NCC), shortlisted four developers and published their proposals for the community to see. Using the criteria presented by the four prequalified proponents, the students were asked to research and propose their own ideas for the space. Using a scale version of the space in Minecraft, the students built their proposed plan for the space in a 1:1 scale replica of LeBreton Flats.
 Date Created:
 20160129

 Resource Type:
 Conference Proceeding
 Creator:
 Bucking, Scott and Cotton, James S.
 Abstract:
 Net zero energy (NZE) communities are becoming pivotal to the energy vision of developers. Communities that produce as much energy as they consume provide many benefits, such as reducing lifecycle costs and better resilience to grid outages. If deployed using smartgrid technology, NZE communities can act as a grid node and aid in balancing electrical demand. However, identifying costeffective pathways to NZE requires detailed energy and economic models. Information required to build such models is not typically available at the early masterplanning stages, where the largest energy and economic saving opportunities exist. Methodologies that expedite and streamline energy and economic modeling could facilitate early decision making. This paper describes a reproducible methodology that aids modelers in identifying energy and economic savings opportunities in the early community design stages. As additional information becomes available, models can quickly be recreated and evaluated. The proposed methodology is applied to the firstphase design of a NZE community under development in Southwestern Ontario.
 Date Created:
 20150101

 Resource Type:
 Conference Proceeding
 Creator:
 Bucking, Scott
 Abstract:
 Energy models are commonly used to examine the multitude of pathways to improve building performance. As presently practiced, a deterministic approach is used to evaluate incremental design improvements to achieve performance targets. However, significant insight can be gained by examining the implications of modeling assumptions using a probabilistic approach. Analyzing the effect of small perturbations on the inputs of energy and economic models can improve decision making and modeler confidence in building simulation results. This paper describes a reproducible methodology which AIDS modelers in identifying energy and economic uncertainties caused by variabilities in solar exposure. Using an optimization framework, uncertainty is quantified across the entire simulation solution space. This approach improves modeling outcomes by factoring in the effect of variability in assumptions and improves confidence in simulation results. The methodology is demonstrated using a net zero energy commercial office building case study.
 Date Created:
 20170101

 Resource Type:
 Conference Proceeding
 Creator:
 Jackson, Edward T. and Schwartz, Karen
 Date Created:
 20080530

 Resource Type:
 Conference Proceeding
 Creator:
 van de Sande, Adje and Schwartz, Karen
 Date Created:
 20080530

 Resource Type:
 Conference Proceeding
 Creator:
 Neely, Colleen, Rumig, Joanne, Taylor, Christine, and Sharp, David
 Abstract:
 Since 2014, Carleton University Library has been adding to the ways it practices collection development. In addition to the subject liaison firm order model, we have added 3 successful usercentred ways to acquire material. We ended our approval plan and used its selection framework to create a DDA plan. We started a textbook purchasing program in Reserves, and we instituted print purchase on demand procedures in ILL. This poster provides an overview and key takeaways for each initiative.
 Date Created:
 20161103

 Resource Type:
 Conference Proceeding
 Creator:
 Cross, Emma, Schramm, Cheryl, Skerlak, Steve, and Tucci, Ryan
 Date Created:
 20160510

 Resource Type:
 Conference Proceeding
 Creator:
 Bucking, Scott
 Abstract:
 Energy modeling and optimization studies can facilitate the design of costeffective, lowenergy buildings. However, this process inevitably involves uncertainties such as predicting occupant behavior, future climate, and econometric parameters. As presently practiced, energy modelers typically do not quantify the implications of these unknowns into performance outcomes. This paper describes an energy modeling approach to quantify economic risk and better inform decision makers of the economic feasibility of a project. The proposed methodology suggests how economic uncertainty can be quantified within an optimization framework. This approach improves modeling outcomes by factoring in the effect of variability in assumptions and improves confidence in simulation results. The methodology is demonstrated using a net zero energy commercial office building case study located in London, ON, Canada.
 Date Created:
 20160101

 Resource Type:
 Conference Proceeding
 Creator:
 Browning, Jennifer
 Abstract:
 The use of open linked data in libraries is quickly developing as means of connecting digital content from the web to local library collections. In the world of cataloguing, metadata, and authority control, using controlled vocabularies through open linked data presents the possibility of providing library patrons with access to a seemingly unlimited expanse of digital resources. Encouraged by this potential, the Carleton University Library is currently implementing open linked data models within its institutional repository in order to connect users to digital content within our repository, our ILS, and beyond. This poster presents the ideas and processes behind this innovative project, and hopes to inspire other libraries to implement open linked data concepts in order to enhance the discoverability of their own digital collections. Learning Outcomes: • Clear explanation of open linked data concepts using diagrams to illustrate key points • How libraries of all sizes can utilize linked data for authority control to expand access to digital collections • How libraries can use linked data to promote and expand access to OA publications
 Date Created:
 20160128

 Resource Type:
 Conference Proceeding
 Creator:
 Rosenbloom, Daniel
 Date Created:
 20170302

 Resource Type:
 Conference Proceeding
 Creator:
 Szyszlo, Peter
 Abstract:
 The purpose of this article is to improve understanding of internationalization as a strategic response to the catalysts of globalization and the knowledge society. The paper will attempt to critically identify and interpret how the aforementioned elements are being recontextualized and translated into responsive internationalization policies and systemic institutional change. The article takes a critical analysis approach on current internationalization efforts and provides a conceptual framework for developing a performance indicator set through a combination of institutional change theory (North 1990) and the Delta cycle for internationalization (Rumbley 2010). Recommendations on future research areas are made at the conclusion of the article.
 Date Created:
 20160101

 Resource Type:
 Conference Proceeding
 Creator:
 Ghandeharian, Sacha
 Date Created:
 20170302

 Resource Type:
 Conference Proceeding
 Creator:
 Kaliberda, Elena
 Date Created:
 20170304