Engineering

As a global feature of fingerprints, the orientation field is very important for automatic fingerprint recognition. Many algorithms have been proposed for orientation field estimation, but their results are unsatisfactory, especially for poor quality fingerprint images. In this paper, a model-based method for the computation of orientation field is proposed. First a combination model is established for the representation of the orientation field by considering its smoothness except for several singular points, in which a polynomial model is used to describe the orientation field globally and a point-charge model is taken to improve the accuracy locally at each singular point. When the coarse field is computed by using the gradient-based algorithm, a further result can be gained by using the model for a weighted approximation. Due to the global approximation, this model-based orientation field estimation algorithm has a robust performance on different fingerprint images. A further experiment shows that the performance of a whole fingerprint recognition system can be improved by applying this algorithm instead of previous orientation estimation methods.

We explore natural and calm interfaces for configuring ubiquitous computing environments. A natural interface should enable the user to name a desired configuration and have the system enact that configuration. Users should be able to use familiar names for configurations without learning, which implies the mapping from names to configurations is many-to-one. Instead of users learning the environment's command language, the system simultaneously learns common configurations and infers the keywords that are most salient to them. We call this the SNAC problem (Simultaneous Naming and Configuration). As a case study, we contrast speech and GUI interfaces for workspace lighting control on a large array of individually-controllable lights. In our design process we have used a lo-fidelity text-based study, a speech-based training data collection study, an evaluation of the deployed live system and are conducting a longer evaluation of the deployed system.

In Active Capture applications, systems that direct human action, the system works with the user to achieve a common goal, for example, taking her picture and recording her name for inclusion on a department web page. The design of Active Capture applications draws from the areas of direction and cinematography, computer vision and audition, and human-computer interaction and results in a diverse design team. Without a

Characterizing the evolution of Internet topology is important to our understanding of the Internet architecture and its interplay with technical, economic and social forces. A major challenge in obtaining empirical data on topology evolution is to identify real topology changes from the observed topology changes, since the latter can be due to either topology changes or transient routing dynamics. In this paper, we formulate the topology liveness problem and propose a solution based on the analysis of BGP data. We find that the impact of transient routing dynamics on topology observation decreases exponentially over time, and that the real topology dynamics consist of a constant-rate birth process and a constant-rate death process. Our model enables us to infer real topology changes from observation data with a given confidence level. We demonstrate the usefulness of the model by applying it to three applications: providing more accurate views of the topology, evaluating theoretical evolution models, and empirically characterizing the trends of topology evolution. We find that customer networks and provider networks have distinct evolution trends, which can provide an important input to the design of future Internet routing architecture.

The Internet AS-level topology is a highly dynamic structure that evolves over time under diverse technical, economical and social forces. Up to now the few efforts on topology visualization have taken only static snapshots of the topology graph. In this poster, we present Cyclops, an interactive visualization tool that highlights the changes in the Internet AS-level topology. We use case studies to demonstrate how Cyclops helps reveal and understand AS topology changes. We also propose a new set of functionalities to be added to Cyclops, which can greatly benefit from the community input and feedback.

A prefix hijack attack involves an attacker announcing victim networks' IP prefixes into the global routing system. As a result, data traffic from portions of the Internet can be diverted to attacker networks. Prefix hijack attacks are a serious security threat in the Internet and it is important to understand the factors that affect the resiliency of victim networks against these attacks. In this paper, we conducted a systematic study to gauge the effectiveness of prefix hijacks launched at different locations in the Internet topology. Our study shows that direct customers of multiple tier-1 networks are the most resilient, even more than the tier-1 networks themselves. Conversely, if these customer networks are used to launch prefix hijacks, they would also be the most effective launching pads for attacks. We verified our results through case studies using real prefix hijack incidents that had occurred in the Internet.

Path vector routing protocols such as the Border Gateway Protocol (BGP) are known to suffer from slow convergence following a change in the network topology or policy. Although a number of convergence enhancements have been proposed recently, there has been no general analytical framework to assess and compare the various proposed algorithms. In this paper we present such a general framework to analyze the upper bounds of path vector protocolsÕ convergence delay under shortest path routing policy and single link failure. Our framework takes into account important factors such as network connectivity, failure location, and routing message processing delay. It can be used to analyze both standard BGP and all the proposed convergence improvement algorithms in the case of shortest path routing policy and single link failure. It enables us to obtain previously unavailable analytical results, including the delay bounds of path fail-over for standard BGP and its convergence enhancements. Our analysis shows that BGP fail-over delay bounds are mainly determined by two factors: (1) the distance between the failure location and the destination, and (2) the length of the longest alternate path to reach the destination after the failure. These two factors are captured formally by our analysis and can explain why existing convergence enhancements often provide only limited improvements in fail-over events. Moreover, explicitly modeling message processing delay reveals insights into the impacts of connectivity richness (i.e., node degree and total number of links in the network), and also the effectiveness of different enhancements. These new results enable one to better understand and compare the behavior of various path vector protocols under different topology structures, network sizes, and message delays.

In this paper we present a troubleshooting tool designed to identify a number of DNS configuration errors. These errors range from commonly seen misconfigurations that are well known among DNS operators, such as lame delegations, to less known ones, such as cyclic zone dependencies. Left unnoticed, these misconfigurations can seriously affect the availability of the DNS infrastructure. Instead of explicitly enumerating all possible configuration errors, we first identify two essential properties that characterize a correct DNS configuration, and detect misconfigurations as violations of these properties. We also utilize multiple monitoring points to identify configuration errors that are difficult or impossible to pin down with a single vantage point. Furthermore, equipped with a comprehensive graphical user interface, our tool provides network operators with a tangible view of their DNS zones' configuration and the errors that may affect their availability.

Traditional routing protocol designs have focused solely on the functionality of the protocols and implicitly assume that all routing update messages received by a router carry valid information. However operational experience suggests that hardware faults, software implementation bugs, operator misconfigurations, let alone malicious attacks can all lead to invalid routing protocol announcements. Although several recent efforts have developed cryptography-based authentication for routing protocols, such enhancements alone are rendered ineffective in the face of faults caused by misconfigurations or hardware/software errors. In this paper we develop a simple routing update validation algorithm for the RIP protocol, RIP with Triangle theorem checking and Probing (RIP-TP). In RIP-TP routers utilize a triangle theorem to identify suspicious new routing announcements, and then use probing messages to verify the correctness of the announcements. We have evaluated the effectiveness of RIP-TP through simulation using various faulty node behaviors, link failure dynamics and network sizes. The results show that, with an overhead as low as about one probing message per received update message in the worst case, RIP-TP can effectively detect 95% or more invalid routing announcements.

The Domain Name System (DNS) is an essential part of the Internet infrastructure and provides fundamental services, such as translating host names into IP addresses for Internet communication. The DNS is vulnerable to a number of potential faults and attacks. In particular, false routing announcements can deny access to the DNS service or redirect DNS queries to a malicious impostor. Due to the hierarchical DNS design, a single fault or attack against the routes to any of the top-level DNS servers can disrupt Internet services to millions of users. In this paper, we propose a path-filtering approach to protect the routes to the critical top-level DNS servers. Our approach exploits both the high degree of redundancy in top-level DNS servers and the observation that popular destinations, including top-level DNS servers, are well-connected via stable routes. Our path-filter restricts the potential top-level DNS server route changes to be within a set of established paths. Heuristics derived from routing operations are used to adjust the potential routes over time. We tested our path-filtering design against BGP routing logs and the results show that the design can effectively ensure correct routes to top-level DNS servers without impacting DNS service availability.

Protocol Boosters are functional elements, inserted and deleted from network protocol stacks on an as-needed basis. The Protocol Booster design methodology attempts to improve end-to-end networking performance by adapting protocols to network dynamics. We describe a new dynamically recon gurable FPGA based architecture, called the Programmable Protocol Processing Pipeline (P4), which provides a platform for highly-exible hardware implementations of Protocol Boosters. The prototype P4 is designed to interface to an OC3 (155 Mb/s) ATM link and perform selected boosting functions at this line rate. The FPGA devices process the data stream as a pipeline of processing elements. Processing elements are downloaded and activated dynamically, based on policies used by the controller to choose con gurations. As modules become unnecessary they are removed from the pipeline chain.

This brief paper outlines our strategies for providing a hardware and software solution to interfacing hosts to high-performance networks. Our prototype implementation connects an IBM RS/6000 to a SONET-based ATM network carrying data at the OC-3c rate of 155 Mbps. We have measured application-to-network data rates of up to 130 Mbps.

Quality of Service (QoS) guarantees for delay sensitive networked multimedia applications, such as teleoperation, must be application-to-application. We describe a set of services, a service kernel, required at the end points, for multimedia call establishment with QoS guarantees. These services provide: (1) Translation among di erent domain speci cations (layerto-layer translation) and domain-resource speci cations (layer-to-resource translation); (2) Admission and Allocation of resources; and (3) Negotiation and Coordination of QoS speci cations among the distributed endpoints. For each service we propose architectural solutions.

The design principle of restricting local autonomy only where necessary for global robustness has led to a scalable Internet. Unfortunately, this scalability and capacity for distributed control has not been achieved in the mechanisms for specifying and enforcing security policies. This shortcoming must be overcome if end-to-end security mechanisms (such as IPsec or TLS) are to ever replace solutions of short-term convenience such as firewalls.

Conventional firewalls rely on topology restrictions and controlled network entry points to enforce traffic filtering. Furthermore, a firewall cannot filter traffic it does not see, so, effectively, everyone on the protected side is trusted. While this model has worked well for small to medium size networks, networking trends such as increased connectivity, higher line speeds, extranets, and telecommuting threaten to make it obsolete.

Z is a softwares ystem designed to provide media-transparent network services on a collection of UNIX®m achines. These services are comprised of file transfer and command execution; Z preserves file ownership on remote transfer,a nd mores ignificantly,o wner and group identity when executing commands remotely.I norder to secureknown vulnerabilities in the system, enhancements werem ade.I np articular,ac ryptographically-derived checksum was added to the messages. After the initial implementation of the checksumming scheme,s everal iterations of performance improvement occurred. The result was unsatisfactory to the user community,s ot he checksum was removed. Instead, vulnerabilities were reduced by improved monitoring and maintenance procedures.

We present techniques for analyzing the effect of ''copy-on-write'' page management strategies on the performance of UNIX fork() operations. The analysis techniques are applied on two workstations, the AT&T 3B2/310 TM and the Hewlett-Packard HP9000/350 TM in order to determine the relationships between the amount of memory in the parent's data segment, the fraction of this memory which is written by the child, and the improvement in execution time due to ''copy-on-write''. Since the implementation of ''copy-on-write'' is straightforward with modern MMUs, our results for these workstations are readily generalized to other workstations.

Software Design Laboratory is an undergraduate practicum in software design, which focuses on principles and practices of large-scale software design. Concepts and examples borrowed from elsewhere in Computer Science are applied to the construction of a significant project, namely a command interpreter resembling the Bourne shell. The course focus is on long-liveds oftware systems of a size requiring group effort. Wet herefore address maintenance, testing, documentation, code readability,version control, and group dynamics.

Byzantine and rational behaviors are increasingly recognized as unavoidable realities in today's cooperative services. Yet, how to design BAR-tolerant protocols and rigorously prove them strategy proof remains somewhat of a mystery: existing examples tend either to focus on unrealistically simple problems or to want in rigor. The goal of this paper is to demystify the process by presenting the full algorithmic development cycle that, starting from the classic synchronous Repeated Terminating Reliable Broadcast (R-TRB) problem statement, leads to a provably BAR-tolerant solution. We show i) how to express R-TRB as a game; ii) why the strategy corresponding to the optimal Byzantine Fault Tolerant algorithm of Dolev and Strong does not guarantee safety when non-Byzantine players behave rationally; iii) how to derive a BAR-tolerant R-TRB protocol: iv) how to prove rigorously that the protocol ensures safety in the presence of non-Byzantine rational players.

We design and evaluate a lightweight route verification mechanism that enables a router to discover route failures and inconsistencies between advertised Internet routes and actual paths taken by the data packets. Our mechanism is accurate, incrementally deployable, and secure against malicious intermediary routers. By carefully avoiding any cryptographic operations in the data path, our prototype implementation achieves the overhead of less than 1% on a 1 Gbps link, demonstrating that our method is suitable even for high-performance networks.

We present the first peer-to-peer data streaming application that guarantees predictable throughput and low latency in the BAR (Byzantine/Altruistic/Rational) model, in which nonaltruistic nodes can behave in ways that are self-serving (rational) or arbitrarily malicious (Byzantine). At the core of our solution is a BARtolerant version of gossip, a well-known technique for scalable and reliable data dissemination. BAR Gossip relies on verifiable pseudo-random partner selection to eliminate non-determinism that can be used to game the system while maintaining the robustness and rapid convergence of traditional gossip. A novel fair enough exchange primitive entices cooperation among selfish nodes on short timescales, avoiding the need for long-term node reputations. Our initial experience provides evidence for BAR Gossip's robustness. Our BAR-tolerant streaming application provides over 99% convergence for broadcast updates when all clients are selfish but not colluding, and over 95% convergence when up to 40% of clients collude while the rest follow the protocol. BAR Gossip also performs well when the client population consists of both selfish and Byzantine nodes, achieving over 93% convergence even when 20% of the nodes are Byzantine.

We describe a family of ÐÓ Ò protocols for assigning symmetric keys to Ò processes in a network so that each process can use its assigned keys to communicate securely with every other process. The -th protocol in our protocol family, where ½ ÐÓ Ò, assigns Ç´ ¾ Ô Òµ symmetric keys to each process in the network. (Thus, our (ÐÓ Ò)-th protocol assigns Ç´ÐÓ ¾ Òµ symmetric keys to each process. This is not far from the lower bound of Ç´ÐÓ Òµ symmetric keys which we show is needed for each process to communicate securely with every other process in the network.) The protocols in our protocol family can be used to assign symmetric keys to the processes in a sensor network, or ad-hoc or mobile network, where each process has a small memory to store its assigned keys. We also discuss the vulnerability of our protocols to "collusion". In particular, we show that Ô Ò colluding processes can compromise the security of the -th protocol in our protocol family.

This paper describes a general approach to constructing cooperative services that span multiple administrative domains. In such environments, protocols must tolerate both Byzantine behaviors when broken, misconfigured, or malicious nodes arbitrarily deviate from their specification and rational behaviors when selfish nodes deviate from their specification to increase their local benefit. The paper makes three contributions: (1) It introduces the BAR (Byzantine, Altruistic, Rational) model as a foundation for reasoning about cooperative services; (2) It proposes a general three-level architecture to reduce the complexity of building services under the BAR model; and (3) It describes an implementation of BAR-B, the first cooperative backup service to tolerate both Byzantine users and an unbounded number of rational users. At the core of BAR-B is an asynchronous replicated state machine that provides the customary safety and liveness guarantees despite nodes exhibiting both Byzantine and rational behaviors. Our prototype provides acceptable performance for our application: our BAR-tolerant state machine executes 15 requests per second, and our BAR-B backup service can back up 100MB of data in under 4 minutes.

Pearling is an interactive technique for extracting the centerline and varying thickness of (hand-drawn) curves in images. It works in realtime, is capable of tracing complex curve networks, and supports gesture-driven interactive editing to trim or extend the selection.

We define b-compatibility for planar curves and propose three 2 ball morphing techniques (b-morphs) between pairs of b-3 compatible curves. B-morphs use the automatic ball-map 4 correspondence, proposed by Chazel et al. [11], from which 5 they derive vertex trajectories (Linear, Circular, Parabolic).

Climate change governance is an emerging topic in the citizen engagement discourse.  This is an Expert Group Meeting (EGM) report focused on the socioeconomic impacts of climate change on citizen engagement that reciprocate creative solutions from the bottom-up in public administration processes.  The EGM held during the World Civic Forum 2009 initiative on May 5 - 8 May 2009 in Seoul, Korea. The overarching theme of the forum was Building Our humanitarian Planet, espoused by three sub-themes: 1. Civic Values for Global Justice; 2. Civic Engagement in Public.  It was agreed that there is a need for UNDESA to boost its activities to enhance citizen engagement to cope with climate change challenges was emphasized during the EGM. Promotion of public awareness, preparedness, adaptation, and mitigation were recognized as critical to success. Over ten concrete policy and programme proposals were identified for further analysis, which will be presented by UNDESA as input to the forthcoming United Nations Climate Change Conference to be held in Copenhagen, 7-18 December 2009, as well as to ECOSOC through its subsidiary body, the Committee of Experts on Pubic Administration (CEPA).

Unashamedly inspired by del.icio.us as we were, we felt there were some additional characteristics of academic reference lists that warranted a separate, tailored service catering to, and making the most of, the needs of the academic community. Therefore, Connotea is a meld of existing reference management conventions and new social bookmarking concepts that are explored in a companion paper . While none of these concepts is original to Connotea, the combination is. To spell them out: 11. GNU General Public License. <http://www.gnu.org/copyleft/gpl.html>.

Observational epidemiological studies suffer from many potential biases, from confounding and from reverse causation, and this limits their ability to robustly identify causal associations. Several high-profile situations exist in which randomized controlled trials of precisely the same intervention that has been examined in observational studies have produced markedly different findings. In other observational sciences, the use of instrumental variable (IV) approaches has been one approach to strengthening causal inferences in non-experimental situations. The use of germline genetic variants that proxy for environmentally modifiable exposures as instruments for these exposures is one form of IV analysis that can be implemented within observational epidemiological studies. The method has been referred to as ‘Mendelian randomization’, and can be considered as analogous to randomized controlled trials. This paper outlines Mendelian randomization, draws parallels with IV methods, provides examples of implementation of the approach and discusses limitations of the approach and some methods for dealing with these.

This paper addresses two major challenges new product development teams face in making a product people want. The first challenge is to frame the design situation based on a real need of a customer. The second, less obvious, challenge is to get everyone on the team in agreement about what that framing is - everyone needs to be on the same page about what it is they're doing. Yet these two challenges are not independent, they are intertwined with each other, connected by the concrete research and sharing activities the teams perform. We introduce a framework to help understand the path of a design team along these two dimensions as well as illustrations of the three most common paths observed among graduate multidisciplinary new product development teams as supported by interviews and survey data. These case studies form the basis of four themes and twelve design principles to help teams navigate the new product development process.

Members of newly formed design teams have different frames – implicit values, goals, and assumptions – they each hold about what problems are important and how they are best addressed. In the early, informal phases of design projects, these frames, and the degree to which they are shared within the team, have substantial consequences. However, little is known about the interactions and activities that reveal frames and support frame sharing in teams.

Our study follows 22 newly-formed multidisciplinary teams through the early phases of the design process in a New Product Development course.  We used a mixed method, inter-disciplinary approach to understand the dynamic process through which design frames are socially negotiated and shared.  We identified core framing activities of design teams and propose a framing cycle of pseudo-frame setting, making individuals’ frames explicit, making frame conflicts salient, and building a common frame.

All learning algorithms attempt to improve the accuracy of a classification system. However, the effectiveness of such a system is dependent on the heuristic used by the learning paradigm to measure performance. This paper demonstrates that the use of Precision (P ) for performance evaluation of imbalanced data sets could lead the solution towards sub-optimal answers. We move onto present a novel performance heuristic, the 'Optimized Precision (OP)', to negate these detrimental effects. We also analyze the impact of these observations on the training performance of ensemble learners and Multi-Classifier Systems (MCS), and provide guidelines for the proper training of multi-classifier systems.

The main challenge in handwritten character recognition involves the development of a method that can generate descriptions of the handwritten objects in a short period of time. Due to its low computational requirement, fuzzy logic is probably the most efficient method available for on-line character recognition. The most tedious task associated with using fuzzy logic for online character recognition involves the building of the rule-base that would describe the characters to be recognized. This problem is further complicated by the fact that different people write the same character in completly different ways. This paper descr ibes a method that can be used to automatically generate a fuzzy membership value database that describes the characters written by different individuals.

The main challenge in handwritten character recognition involves the development of a method that can generate descriptions of the handwritten objects in a short period of time. Due to its low computational requirement, fuzzy logic is probably the most efficient method available for on-line character recognition. The most tedious task associated with using fuzzy logic for online character recognition is the building of the rule-base that would describe the characters to be recognized. The problem is complicated as different people write the same character in complete different ways. This paper describes a method that can be used to generate a fuzzy value database that describes the characters written by different individuals.

Handwritten characters differ from person to person. Thus, when using traditional methods like Neural Networks and Image Processing techniques, extensive training of the system is needed. Due to this reason, an attempt was made to develop a system that used the methods that humans use to perceive handwritten characters. Thus, a system that recognizes features in handwritten characters using Fuzzy Logic was developed. The reasons for the selection of Fuzzy Logic were as follows: 1. Fuzzy Logic can be used to model human perception 2. The mathematics that Fuzzy Logic requires is extremely fundamental. Thus, any algorithm developed using fuzzy logic would require relatively simple and short calculations. 3. Due to simplicity of fuzzy calculations, they can be implemented on any hardware or software platform without too much concern for computing power. The objectives in the development of this method were: 1. The development of a short and efficient algorithm that tries as much as possible to model human perception. 2. The development of an algorithm that can be implemented on any hardware or software platform through low computational power requirements. A time ordered sequence of coordinates should be sent into the system. The following calculations are then preformed on this set of data: 1. Segmentation of the image based on the direction of movement 2. Determination of the universe of discourse 3. Calculation of the local features for each identified segment 4. Application to Fuzzy Rule-Base for character recognition.

Handwritten characters differ from person to person. Thus, when using traditional methods like Neural Networks and Image Processing techniques, extensive training of the system is needed. Due to this reason, an attempt was made to develop a system that used the methods that humans use to perceive handwritten characters. Thus, a system that recognizes features in handwritten characters using Fuzzy Logic was developed. The reasons for the selection of Fuzzy Logic were as follows: 1. Fuzzy Logic can be used to model human perception 2. The mathematics that Fuzzy Logic requires is extremely fundamental. Thus, any algorithm developed using fuzzy logic would require relatively simple and short calculations. 3. Due to simplicity of fuzzy calculations, they can be implemented on any hardware or software platform without too much concern for computing power. The objectives in the development of this method were: 1. The development of a short and efficient algorithm that tries as much as possible to model human perception. 2. The development of an algorithm that can be implemented on any hardware or software platform through low computational power requirements.