The Computer Journal - Advance Access

Detecting Common Modules in Java Packages Based on Static Object Trace Birthmark

Park, H., Lim, H.-i., Choi, S., Han, T. — Thu, 05 Nov 2009 04:48:31 PST

A software birthmark means inherent characteristics that can be used to identify a program. In this paper, we propose a birthmark technique based on object traces of Java programs. Java is an object-oriented programming language that provides various predefined class libraries that help programmers to produce software easily. In order to utilize Java class libraries, we have to use Java object instructions. The Java object instructions are hard to replace or remove, and so a set of sequences of object instructions is a proper candidate to represent inherent characteristics of a program. We propose a new birthmark using the sequences of object instructions. We evaluate the proposed birthmark with open source programs and compare it with previous static birthmarks. Experiments show that the detection capability of our birthmark is much higher than that of other static birthmarks despite obfuscations by Smokescreen and ZKM.

New Benchmarks for Large-Scale Networks with Given Maximum Degree and Diameter

Loz, E., Pineda-Villavicencio, G. — Wed, 04 Nov 2009 07:45:05 PST

Large-scale networks have become ubiquitous elements of our society. Modern social networks, supported by communication and travel technology, have grown in size and complexity to unprecedented scales. Computer networks, such as the Internet, have a fundamental impact on commerce, politics and culture. The study of networks is also central in biology, chemistry and other natural sciences. Unifying aspects of these networks are a small maximum degree and a small diameter, which are also shared by many network models, such as small-world networks. Graph theoretical methodologies can be instrumental in the challenging task of predicting, constructing and studying the properties of large-scale networks. This task is now necessitated by the vulnerability of large networks to phenomena such as cross-continental spread of disease and botnets (networks of malware). In this article, we produce the new largest known networks of maximum degree 17 ≤ ≤ 20 and diameter 2 ≤ D ≤ 10, using a wide range of techniques and concepts, such as graph compounding, vertex duplication, Kronecker product, polarity graphs and voltage graphs. In this way, we provide new benchmarks for networks with given maximum degree and diameter, and a complete overview of state-of-the-art methodology that can be used to construct such networks.

Growing Software: Proven Strategies for Managing Software Engineers

Harrin, E. — Tue, 03 Nov 2009 07:59:23 PST

Security Metrics Foundations for Computer Security

Trcek, D. — Tue, 03 Nov 2009 07:59:22 PST

Security has been among top priority in computer information systems for more than a decade. Despite the importance of this area, it is interesting to note that the area still lacks (completeness of) one of its basic elements of scientific arsenal, which is metric. This paper therefore presents the situation in this field by giving an analysis of existing metrics that could serve the above-mentioned purpose. Further, it presents a generic risk management model, and gives an analysis of possibilities for application of these existing metrics to the model. It also introduces new metric elements, where these are lacking. As a result, means are provided that enable evaluation of security in information technology systems in a tangible way. Such an approach is essential for every organization in business areas ranging from economical justifications for new security implementations to customized security services with appropriate service costs calculations, and even development of new business models.

A Unified Theory of Program Logics: An Approach based on the {pi}-Calculus

Honda, K., Yoshida, N. — Tue, 03 Nov 2009 07:59:22 PST

Facing staggering diversity of software behaviours in modern and future computing, we argue for the need of a unified theory of program logics, which can capture a general class of software behaviours, as a foundation of software engineering. We propose Hennessy–Milner logic for typed -calculi as a possible foundation of such a theory. The -calculus is in a singular position among computational calculi through its ability to embed sequential and concurrent programs as name passing processes without losing semantic information, and through its connection to other basic semantic theories such as linear logic and game semantics. The embedding of programs in processes leads to the embedding of program logics in the process logic, where the observational content of a given program logic is made explicit, analysed and justified on a uniform basis. As a case study, we show embedding of Hoare logic for sequential programs and a rely-guarantee logic for shared variable concurrency, suggesting that the proposed framework can offer a unifying basis to capture fundamental notions in program logics such as partial/total correctness, sequentiality and different kinds of concurrent computing.

A Methodological Construction of an Efficient Sequentially Consistent Distributed Shared Memory

Cholvi, V., Fernandez, A., Jimenez, E., Manzano, P., Raynal, M. — Tue, 03 Nov 2009 07:59:21 PST

The paper proposes a simple protocol that ensures sequential consistency. The protocol assumes that the shared memory abstraction is supported by the local memories of nodes that can communicate only by exchanging messages through reliable channels. Unlike other sequential consistency protocols, the one proposed here does not rely on a strong synchronization mechanism, such as an atomic broadcast primitive or a central node managing a copy of every shared object. From a methodological point of view, the protocol is built incrementally starting from the very definition of sequential consistency. It has the noteworthy property that a process that issues a write operation never has to wait for other processes. Depending on the current local state, most read operations issued also have the same property.

A Case Study Using a Methodological Approach to Developing User Interfaces for Elderly and Disabled People

Picking, R., Robinet, A., Grout, V., McGinn, J., Roy, A., Ellis, S., Oram, D. — Fri, 23 Oct 2009 05:59:36 PDT

In this paper, we present a case study on the development of interfaces for elderly and disabled users. The domain of the case study was situated in the home environment, where we focused on producing affordable technologies to enable users to interact with and to control home appliances. We have developed ambient user interfaces that are integrated in familiar home artefacts, such as televisions and digital picture frames. These interfaces are connected remotely to a home network and are adaptive to users’ expected increasing physical and cognitive needs. To support the development of the project, we created a novel methodology that is grounded in the ethical issues associated with a project of this nature. Our success with it has led to us presenting it here as a practical approach to developing user interfaces for a range of interactive applications, especially where there may be diverse user populations. This paper describes our journey through this project, how the methodology has been used throughout and the development of our user interfaces and their evaluation.

Resampling Halftone Images Using Interpolation and Error-Diffusion

Feng, J.-B., Lin, I.-C., Chu, Y.-P., Tsaur, S.-C. — Mon, 14 Sep 2009 00:12:42 PDT

Halftoning schemes are developed for reserving the quality after transforming continuous tone images to binary images under human vision, and are widely used in printing and outputting. Modern halftoning schemes focus on transforming forward and backward the two kinds of images, but basic operations for halftone images like rescaling, blurring and sharpening are still insufficient. In this paper, a novel halftone image resampling scheme based on interpolation and error-diffusion is proposed. The proposed scheme can shrink and magnify halftone images to any desired scale and does not limit the source of the halftone images. To obtain the best performance, an evaluation tool is proposed to test various combinations of interpolation techniques and error-diffusion kernels. Due to the lack of evaluation research, the evaluation metric called light invariance is developed to evaluate the consistency before and after resampling. By the proposed scheme, resampling halftone images does not need transforming to and back from continuous-tone images anymore.

Area-Feature Boundary Labeling

Bekos, M. A., Kaufmann, M., Potika, K., Symvonis, A. — Fri, 11 Sep 2009 03:02:02 PDT

Boundary labeling is a relatively new labeling method. It can be useful in automating the production of technical drawings and medical drawings, where it is common to explain certain parts of the drawing with text labels, arranged on its boundary so that other parts of the drawing are not obscured. In boundary labeling, we are given a rectangle R which encloses a set of n sites. Each site s is associated with an axis-parallel rectangular label l_s. The labels must be placed in distinct positions on the boundary of R and they must be connected to their corresponding sites with polygonal lines, called leaders, so that the labels are pairwise disjoint and the leaders do not intersect each other. In this paper, we study a version of the boundary labeling problem where the sites can ‘float’ within a polygonal region. We present a polynomial time algorithm, which runs in O(n³) time and produces a labeling of minimum total leader length for labels of uniform size placed in fixed positions on the boundary of rectangle R.

Accelerating Multiple Sequence Alignment with the Cell BE Processor

Vandierendonck, H., Rul, S., De Bosschere, K. — Fri, 11 Sep 2009 03:02:02 PDT

The Cell Broadband Engine (BE) Architecture is a new heterogeneous multi-core architecture targeted at compute-intensive workloads. The architecture of the Cell BE has several features that are unique in high-performance general-purpose processors, most notably the extensive support for vectorization, scratch pad memories and explicit programming of direct memory accesses (DMAs) and mailbox communication. While these features strongly increase programming complexity, it is generally claimed that significant speedups can be obtained by using Cell BE processors. This paper presents our experiences with using the Cell BE architecture to accelerate Clustal W, a bio-informatics program for multiple sequence alignment. We report on how we apply the unique features of the Cell BE to Clustal W and how important each is in obtaining high performance. By making extensive use of vectorization and by parallelizing the application across all cores, we demonstrate a speedup of 24.4 times when using 16 synergistic processor units on a QS21 Cell Blade compared to single-thread execution on the power processing unit. As the Cell BE exploits a large number of slim cores, our highly optimized implementation is just 3.8 times faster than a 3-thread version running on an Intel Core2 Duo, as the latter processor exploits a small number of fat cores.

Task Allocation and Optimization of Distributed Embedded Systems with Simulated Annealing and Geometric Programming

He, X., Gu, Z., Zhu, Y. — Fri, 11 Sep 2009 03:02:01 PDT

We consider the task model of periodic tasks running on a network of processor nodes connected by a bus based on the time-triggered protocol, an industry-standard bus protocol designed for safety-critical automotive and avionics distributed embedded systems, and present an integrated optimization framework that jointly considers one or more of the following attributes: task-to-processor allocation, task priority assignment, task period assignment and bus access configuration. We adopt a hierarchical optimization framework, where each possible task allocation and priority assignment is treated as one top-level coarse-grained state, which may contain many lower-level fine-grained states defined by different task period assignments and bus access configurations. Simulated annealing is used to explore the top-level states, which calls a geometric programming solver as a subroutine to explore the lower-level states contained within a given top-level state. Performance evaluation shows that our framework has good performance in terms of solution quality and scalability.

An ID-Based Mutual Authentication and Key Exchange Protocol for Low-Power Mobile Devices

Wu, T.-Y., Tseng, Y.-M. — Sun, 06 Sep 2009 23:30:04 PDT

The identity (ID)-based public-key system using bilinear pairings defined on elliptic curves offers a flexible approach to simplify the certificate management. In 2006, the IEEE P1363.3 committee has defined the ID-based public-key system with bilinear pairings as one of public-key cryptography standards. In this, an authenticated key agreement (AKA) protocol is one important issue that provides mutual authentication and key exchange between two parties. Owing to the fast growth of mobile networks, the computational cost on the client side with low-power computing devices is a critical factor in designing an AKA protocol suited for mobile networks. In this paper, we present an efficient and secure ID-based mutual authentication and key exchange protocol using bilinear pairings. Performance analysis and experimental data are given to demonstrate that our proposed protocol is well suited for a client–server environment with low-power mobile devices. In comparison with the recently proposed ID-based protocols, our protocol has the best performance on the client side.

Adaptive Random Re-Routing for Differentiated QoS in Sensor Networks

Gelenbe, E., Ngai, E. — Thu, 03 Sep 2009 00:53:33 PDT

Sensor networks (SNs) consist of spatially distributed sensors which monitor an environment, and which are connected to some sinks or backbone system to which the sensor data is being forwarded. In many cases, the sensor nodes themselves can serve as intermediate nodes for data coming from other nodes, on the way to the sinks. Much of the traffic carried by SNs will originate from routine measurements or observations by sensors that monitor a particular situation, such as the temperature and humidity in a room or the infrared observation of the perimeter of a house, so that the volume of routine traffic resulting from such observations may be quite high. When important and unusual events occur, such as a sudden fire breaking out or the arrival of an intruder, it will be necessary to convey this new information very urgently through the network to a designated set of sink nodes where this information can be processed and dealt with. This paper addresses the important challenge by avoiding the routine background traffic from creating delays or bottlenecks that impede the rapid delivery of high priority traffic resulting from the unusual events. Specifically we propose a novel technique, the ‘Randomized Re-Routing Algorithm (RRR)’, which detects the presence of novel events in a distributed manner, and dynamically disperses the background traffic towards secondary paths in the network, while creating a ‘fast track path’ which provides better delay and better quality of service (QoS) for the high priority traffic which is carrying the new information. When the surge of new information has subsided, this is again detected by the nodes and the nodes progressively revert to best QoS or shortest-path routing for all the ongoing traffic. The proposed technique is evaluated using a mathematical model as well as simulations, and is also compared with a standard node by a node priority scheduling technique.

Sequence of Control in S3PMR

Shih, Y.-Y., Chao, D. — Thu, 03 Sep 2009 00:53:33 PDT

Huang et al. propose a more permissive siphon-based algorithm for deadlock prevention of a subclass of Petri nets, S³PMR. It iteratively (based on a mixed integer programming (MIP) technique) adds two kinds of control places called ordinary control (OC) places and weighted control (WC) places to the original model to prevent siphons from becoming unmarked. Numerical experiments indicate that the proposed policy appears to be more permissive than closely related approaches in the literature. The presence of WC renders the net a generalized Petri net, which is harder to analyze, and it is unclear how the above traditional MIP must be modified. We show that all monitors with WC places in all cases presented are redundant and can be removed while maintaining the maximal number of good states. We also (1) show that OC places and WC places are associated with resource and mixture siphons, respectively; (2) identify the condition and examples for a WC places to be redundant; (3) explore different types of problematic siphons; and (4) identify the correct sequence of adding monitors to avoid redundant monitors.

Management of Server Farms for Performance and Profit

Mitrani, I. — Thu, 03 Sep 2009 00:53:32 PDT

We examine some of the problems associated with managing a server farm, that is, a collection of servers which are used to provide different types of services to paying customers. The users are charged for the services provided, but are also promised that certain Quality-of-Service (QoS) criteria will be met. Failure to satisfy those QoS undertakings incurs pre-specified penalties. In order to maximize the revenue obtained, the service provider must employ intelligent dynamic policies dealing with server allocation and job admission decisions. A number of such policies are surveyed.

Discussant of Response to the Computer Journal Lecture by Morris Sloman

Milner, R. — Wed, 02 Sep 2009 03:39:44 PDT

A Weighted Voting-Based Associative Classification Algorithm

Zhu, X., Song, Q., Jia, Z. — Tue, 25 Aug 2009 07:02:33 PDT

A new associative classification algorithm based on weighted voting (ACWV) is presented. ACWV takes advantage of two methods: the optimal rule method preferring high-quality rules and the voting method considering the majority of the rules. Moreover, the method takes into account both the length and convictions of rules to calculate their weights. First, ACWV builds a class-count FP-tree (called CCFP-tree) from the given historical data. After that, the weighted voting result for a new instance can be obtained from the CCFP-tree directly without storing, retrieving and sorting rules explicitly. The label of the class with maximal sum of weighted votes is then that of the new instance. Results of the experiments with 36 data sets selected from the UCI machine learning repository show that the proposed method has its advantages in comparison with previous methods in terms of classification accuracy.

Hardness Results and Heuristic for Multi-groups Interconnection

Blin, L., Laforest, C., Rovedakis, S., Thibault, N. — Fri, 21 Aug 2009 04:59:45 PDT

This paper is dedicated to the connection, by a provider, of multiple groups of nodes spread over a network. The role of the provider is to interconnect the members of every group. For this purpose, it must distribute the available links of the network between the groups. The general aim then is to allocate these links in such a way that the communications latencies in the allocated structure are equivalent to the ones in the original (full) network for each group. We study two approaches constructing structures preserving the maximum latency (called the diameter). Unfortunately we show that the associated optimization graph problems are difficult (one cannot be approximated by a constant and the other is NP-complete). Due to these difficulties we relax the constraint on the diameter and propose to construct a unique tree connecting all the groups together. We give a heuristic to treat this problem and we propose several analytical results on its maximum and average latencies performance.

Energy-Efficient Cloud Computing

Wed, 19 Aug 2009 03:05:54 PDT

Energy efficiency is increasingly important for future information and communication technologies (ICT), because the increased usage of ICT, together with increasing energy costs and the need to reduce green house gas emissions call for energy-efficient technologies that decrease the overall energy consumption of computation, storage and communications. Cloud computing has recently received considerable attention, as a promising approach for delivering ICT services by improving the utilization of data centre resources. In principle, cloud computing can be an inherently energy-efficient technology for ICT provided that its potential for significant energy savings that have so far focused on hardware aspects, can be fully explored with respect to system operation and networking aspects. Thus this paper, in the context of cloud computing, reviews the usage of methods and technologies currently used for energy-efficient operation of computer hardware and network infrastructure. After surveying some of the current best practice and relevant literature in this area, this paper identifies some of the remaining key research challenges that arise when such energy-saving techniques are extended for use in cloud computing environments.

Protection Against Denial of Service Attacks: A Survey

Loukas, G., Oke, G. — Wed, 19 Aug 2009 03:05:53 PDT

Denial of service (DoS) is a prevalent threat in today's networks because DoS attacks are easy to launch, while defending a network resource against them is disproportionately difficult. Despite the extensive research in recent years, DoS attacks continue to harm, as the attackers adapt to the newer protection mechanisms. For this reason, we start our survey with a historical timeline of DoS incidents, where we illustrate the variety of types, targets and motives for such attacks and how they evolved during the last two decades. We then provide an extensive literature review on the existing research on DoS protection with an emphasis on the research of the last years and the most demanding aspects of defence. These include traceback, detection, classification of incoming traffic, response in the presence of an attack and mathematical modelling of attack and defence mechanisms. Our discussion aims to identify the trends in DoS attacks, the weaknesses of protection approaches and the qualities that modern ones should exhibit, so as to suggest new directions that DoS research can follow.

Sensornet Protocol Tuning Using Principled Engineering Methods

Tate, J., Bate, I. — Wed, 19 Aug 2009 01:26:37 PDT

Sensornet designers seek to maximize energy efficiency while maintaining acceptable Quality of Service. However, the interactions between multiple tunable protocol parameters and multiple performance metrics are generally complex and unknown, and combinatorial explosion renders impossible any exhaustive search approach. Most work published to date employs seemingly arbitrary choices of protocol parameters, derived by informal judgement and limited trial and error experiments. This lack of rigour may lead to sub-optimal parameter selection and sub-optimal network behaviour, and may mask the real performance differences of dissimilar protocols. We describe a reusable engineering method to address this multi-dimensional optimization problem, based on sound engineering principles widely recognized and applied beyond Computer Science. We provide a mechanism with which to de-risk deployment of sensornets tuned within training environments, and evaluate the robustness of these tunings to changing environments. The mechanism is also useful for comparative evaluation of protocols within a fixed deployment context.

A Bandwidth-Based Power-Aware Routing Protocol with Low Route Discovery Overhead in Mobile Ad hoc Networks

Weng, C.-C., Chen, C.-W., Ku, C.-J., Hwang, S.-F. — Wed, 19 Aug 2009 01:26:36 PDT

In the design of power-aware on-demand routing protocols in mobile ad hoc networks, it must be taken into account that nodes may use a great amount of power to find the desired routing path during the path-discovery phase. In addition, in previous research on power-aware routing protocols, the path bandwidth was often not considered. In this paper, we tackle these issues by proposing a power-aware routing protocol with low route requests (LRR) to find a path with high path bandwidth. By making a low number of routing requests (RREQs), mobile nodes help to broadcast the routing request only when they first receive the routing requests. In addition, based on the receipt of the routing requests from the neighboring nodes, mobile nodes record the location information of its one-hop neighboring nodes. In the path-reply phase, mobile nodes in the found path use the collected location information of their neighbors and our proposed relay model to modify the found path so that the found path has high bandwidth. In our simulation, we compared our proposed routing protocol (LRR) with ad hoc on-demand distance vector, dynamic source routing and min–max battery capacity routing in terms of the following: power consumption in the path-discovery phase and the path-reply phase, bandwidth of the found path, power consumed during data transmission and overall power consumption. In addition, we compared our two proposed routing protocols, the minimum power consumption routing protocol that selects one path with minimum transmission power from all paths and the LRR routing protocol, in terms of the following: the power consumption in the path-discovery phase, the path bandwidth and the overall power consumption. From the simulation results and the analysis, we can see that the proposed LRR routing protocol that uses a low number of routing requests and our proposed relay model to improve path bandwidth can efficiently reduce the overall power consumption.

Fault Coverage-Driven Incremental Test Generation

Simao, A., Petrenko, A. — Wed, 12 Aug 2009 00:50:42 PDT

In this paper, we consider a classical problem of complete test generation for deterministic finite-state machines (FSMs) in a more general setting. The first generalization is that the number of states in implementation FSMs can even be smaller than that of the specification FSM. Previous work deals only with the case when the implementation FSMs are allowed to have the same number of states as the specification FSM. This generalization provides more options to the test designer: when traditional methods trigger a test explosion for large specification machines, tests with a lower, but yet guaranteed, fault coverage can still be generated. The second generalization is that tests can be generated starting with a user-defined test suite, by incrementally extending it until the desired fault coverage is achieved. Solving the generalized test derivation problem, we formulate sufficient conditions for test suite completeness weaker than the existing ones and use them to elaborate an algorithm that can be used both for extending user-defined test suites to achieve the desired fault coverage and for test generation. We present the experimental results that indicate that the proposed algorithm allows obtaining a trade-off between the length and fault coverage of test suites.

'MotorcycleSim': An Evaluation of Rider Interaction with an Innovative Motorcycle Simulator

Fri, 07 Aug 2009 04:20:32 PDT

This paper describes a user-centred design process that has been used to develop an innovative simulator for research into motorcycle ergonomics and rider human factors. Building on initial user requirements and user experience elicitation exercises, an evaluation was conducted to investigate specific issues associated with simulator fidelity. An experimental approach was employed to examine the physical and functional fidelity of the simulator. Using different steering and visual feedback configurations, a battery of objective and subjective dependent variables were analysed including: user perceptions and preferences, rider performance data, rider workload, rider comfort issues and the first evaluation of simulator sickness for a motorcycle simulator. The results indicated that across a number of measures, aspects of functional fidelity were considered more important than the physical fidelity of the simulator. This evaluation takes the development of the simulator a stage further and the paper provides recommendations for future improvements.

On Using Physical Analogies for Feature and Shape Extraction in Computer Vision

Nixon, M. S., Liu, X. U., Direkoglu, C., Hurley, D. J. — Fri, 07 Aug 2009 04:20:31 PDT

There is a rich literature of approaches to image feature extraction in computer vision. Many sophisticated approaches exist for low- and for high-level feature extraction but can be complex to implement with parameter choice guided by experimentation, but with performance analysis and optimization impeded by speed of computation. We have developed new feature extraction techniques on notional use of physical paradigms, with parametrization aimed to be more familiar to a scientifically trained user, aiming to make best use of computational resource. This paper is the first unified description of these new approaches, outlining the basis and results that can be achieved. We describe how gravitational force can be used for low-level analysis, while analogies of water flow and heat can be deployed to achieve high-level smooth shape detection, by determining features and shapes in a selection of images, comparing results with those by stock approaches from the literature. We also aim to show that the implementation is consistent with the original motivations for these techniques and so contend that the exploration of physical paradigms offers a promising new avenue for new approaches to feature extraction in computer vision.

Cheating Immune Threshold Visual Secret Sharing

De Prisco, R., De Santis, A. — Wed, 29 Jul 2009 07:18:08 PDT

In this paper, we consider the problem of cheating for visual cryptography schemes. Although the problem of cheating has been extensively studied for secret sharing schemes, little work has been done for visual secret sharing. We provide a formal definition of cheating for visual cryptography and new (2, n)-threshold and (n, n)-threshold schemes that are immune to deterministic cheating.

Social Networks: An Introduction

Levene, M. — Thu, 23 Jul 2009 06:23:37 PDT

Multi-criteria Scheduling of Precedence Task Graphs on Heterogeneous Platforms

Benoit, A., Hakem, M., Robert, Y. — Wed, 22 Jul 2009 07:48:21 PDT

Latency, fault tolerance and reliability are important requirements for several applications that are time critical in nature: such applications require guarantees in terms of latency, even when processors are subject to failures. In this paper, we propose a fault-tolerant scheduling heuristic for mapping precedence task graphs on heterogeneous systems. Our approach is based on an active replication scheme, capable of supporting arbitrary fail-silent/fail-stop processor failures, and hence valid results will be provided even if processors fail. First we focus on a bi-criteria approach, where we aim at minimizing the latency given a fixed number of failures supported in the system, or the other way round. Next we derive a more complex algorithm in which we not only minimize latency and support a fixed number of failures, but also improve the overall reliability. Major achievements include low complexity of the new algorithms, and a drastic reduction of the number of additional communications induced by the replication mechanism. Experimental results demonstrate that our heuristics, despite their lower complexity, outperform their direct competitor, the fault-tolerance based active replication scheduling algorithm FTBAR.

Introduction to the Special Issue on Advances in Sensing, Information Processing and Decision Making for Coalition Operations within the US/UK International Technology Alliance

Wed, 22 Jul 2009 19:04:34 PDT

Response to Prof. Baccelli's lecture on Modelling of Wireless Communication Networks by Stochastic Geometry

Konstantopoulos, T. — Mon, 13 Jul 2009 02:33:19 PDT

Discussant of Response to the Computer Journal Lecture by Francois Baccelli

Penrose, M. D. — Mon, 13 Jul 2009 02:33:19 PDT

NIPSOM: Parallel Architecture and Implementation of a Growing SOM

Valova, I., Beaton, D., MacLean, D., Hammond, J. — Sat, 11 Jul 2009 04:35:36 PDT

This work describes a parallel implementation of a distinctly different concept in self-organizing maps (SOMs)—processing of the input as a whole, in parallel, via neurons attracted to cover regions of the input space rather than single input instances. The algorithm is analyzed from the perspective of its parallelism and a simple multi-machine concept is utilized to demonstrate the parallel nature of the neural network architecture. The nature of the classic SOM (Ozdzynski, P., Lin, A., Liljeholm, M. and Beatty, J. (2002) A parallel implementation of Kohonen's self-organizing map algorithm: performance and scalability. Neurocomputing, 44–46, 567–571) algorithm displays some parallel characteristics, but contains several bottlenecks, which prevent a true parallel execution. Most SOM parallel implementations either deal with expensive hardware that requires considerable algorithm adaptation, or run multiple instances of SOM on multiple machines and choose the most relevant, or adopt controller–worker architecture with the controller machine presenting a significant bottleneck in the parallelism. Our algorithm (Valova, I., Szer, D., Gueorguieva, G. and Buer, A. (2005) A parallel growing architecture for self-organizing maps with unsupervised learning. Neurocomputing, 68C, 177–195), which we eventually named ParaSOM, reveals no need for significant adaptation to be ported to parallelism and the analysis and implementations we discuss illustrate this quality. This work presents two designs for parallelizing our algorithm and analyzes both while demonstrating the easiness in the transition to a parallel paradigm. We have illustrated the performance gain of the proposed implementation and compared it with other similar methods, from the perspectives of both parallelism and nature of the mapping algorithm.

Hierarchical Radiosity for Multiresolution Systems Based on Normal Tests

Padron, E. J., Amor, M., Boo, M., Doallo, R. — Sat, 11 Jul 2009 04:35:36 PDT

The hierarchical radiosity algorithm provides high-quality illumination and the view-independent results obtained can be re-employed for different camera positions. On the other hand, the utilization of multiresolution models is a common solution for the real-time rendering of complex scenes. In this case, the level of detail of each object depends on the specific camera position. Unfortunately, global illumination computations may present an important performance loss in this context. In this paper we present a new solution for hierarchical radiosity for multiresolution systems. Our proposal is based on the application of an enriched hierarchical radiosity algorithm to an input scene with low-resolution objects (represented by coarse meshes) and the efficient data management of the resulting values. The representation of the information we use permits the application of the radiosity values obtained for the coarse version of an object to finer resolution versions of that object. Results of our implementation show that our algorithm produces high-quality images with an important reduction in computational costs.

Events, Causality and Symmetry

Winskel, G. — Sat, 11 Jul 2009 04:35:35 PDT

The article discusses causal models, such as Petri nets and event structures, how they have been rediscovered in a wide variety of recent applications and why they are fundamental to computer science. A discussion of their present limitations leads to their extension with symmetry. The consequences, actual and potential, are discussed.

On the Usefulness of Fibonacci Compression Codes

Klein, S. T., Ben-Nissan, M. K. — Sat, 11 Jul 2009 04:35:35 PDT

Recent publications advocate the use of various variable length codes for which each codeword consists of an integral number of bytes in compression applications using large alphabets. This paper shows that another tradeoff with similar properties can be obtained by Fibonacci codes. These are fixed codeword sets, using binary representations of integers based on Fibonacci numbers of order m ≥ 2. Fibonacci codes have been used before, and this paper extends previous work presenting several novel features. In particular, the compression efficiency is analyzed and compared to that of dense codes, and various table-driven decoding routines are suggested.

Efficient On-line/Off-line Signature Schemes Based on Multiple-Collision Trapdoor Hash Families

Harn, L., Hsin, W.-J., Lin, C. — Sat, 11 Jul 2009 04:35:35 PDT

The first on-line/off-line signature scheme introduced by Even et al. in 1990 has two problems: (a) impractical signature length and (b) a one-time use of signature generated during the off-line phase. In 2001, Shamir and Tauman significantly shortened the length of the signature by using trapdoor hash families introduced by Krawczyk and Rabin in 2000. However, each trapdoor hash value and its signature in the off-line phase of Shamir and Tauman's signature scheme can be used for signing only one message in the on-line phase. In this paper, we propose multiple-collision trapdoor hash families based on discrete logarithm and factoring assumptions, and provide formal proofs of their security. We also introduce an efficient on-line/off-line signature scheme based on our proposed trapdoor hash families. Our on-line/off-line signature scheme can re-use a trapdoor hash value for signing multiple messages. If a signer includes this trapdoor hash value in the public-key digital certificate, there is no need to have any regular digital signature scheme to sign the trapdoor hash value in the off-line phase.

Analyzing Team Decision-Making in Tactical Scenarios

Sukthankar, G., Sycara, K. — Sat, 11 Jul 2009 04:35:34 PDT

Team decision-making is a bundle of interdependent activities that involve gathering, interpreting and exchanging information; creating and identifying alternative courses of action; choosing among alternatives by integrating the often different perspectives of team members and implementing a choice and monitoring its consequences. To accomplish joint tasks, human team members often assume distinctive roles in task completion. We believe that to design and build software agents that can assist human teams, we need develop automated techniques to identify the roles of the human decision-makers. If the supporting agents are insensitive to shifts in the team's roles, they cannot effectively monitor the team's activities. This article addresses the problem of doing offline role analysis of battle scenarios from multi-player team games. The ability to identify team roles from observations is important for a wide range of applications including automated commentary generation, game coaching and opponent modeling. We define a role as a preference model over possible actions based on the game state. This article explores two promising approaches for automated role analysis: (1) a model-based system for combining evidence from observed events using the Dempster–Shafer theory and (2) a data-driven discriminative classifier using support vector machines.

Program Analysis Probably Counts: Discussant Contribution for the Computer Journal Lecture by Chris Hankin

Malacaria, P. — Sat, 11 Jul 2009 04:35:34 PDT

Two Decades of Random Neural Networks

Kocak, T. — Fri, 10 Jul 2009 07:59:25 PDT

Robust Super-Peer-Based P2P File-Sharing Systems

Lin, J.-W., Yang, M.-F. — Wed, 01 Jul 2009 01:11:08 PDT

This paper presents an efficient approach for improving file availability in super-peer-based peer-to-peer (P2P) file-sharing systems. In the super-peer-based P2P file-sharing system, peers are organized into multiple groups. In each group, there is a special peer called super-peer to serve the regular peers within the same group. With this property, the proposed approach utilizes the super-peer to tolerate the departure (failure) of a regular peer in order to protect shared files. Unlike traditional replication-based approaches, the proposed approach keeps track of the file queries in the super-peer to support fault tolerance. The cost of tracking the file queries is much smaller than the cost of replicating the file contents in advance. Furthermore, the proposed approach uses a logical connection technique to consider the departure (failure) of the super-peer. Finally, simulation experiments are performed to quantify the performance and overhead of the proposed approach.

Understanding the Quality of Monitoring for Network Management

Fri, 26 Jun 2009 01:32:35 PDT

The vitality and utility of a network are affected significantly by the network management system (NMS) that is used to administer and monitor the network. However, models that can characterize the quality of a NMS are generally missing in the literature. In this paper, we introduce the concept of quality of monitoring (QoM), provide a mathematical formulation based on stochastic processes that can be used to model a network monitoring system and define QoM metrics based on this formulation. A formal analysis of the proposed framework along various metrics is also provided, along with a case study of its application to network monitoring in a mobile ad hoc network.

Digital Watermarking and Steganography: Fundamentals and Techniques

Johnson, N. F. — Fri, 26 Jun 2009 01:32:35 PDT

Agent Support for Policy-Driven Collaborative Mission Planning

Wed, 24 Jun 2009 00:24:57 PDT

In this paper, we describe how agents can support collaborative planning within international coalitions, formed in an ad hoc fashion as a response to military and humanitarian crises. As these coalitions are formed rapidly and without much lead time or co-training, human planners may be required to observe a plethora of policies that direct their planning effort. In a series of experiments, we show how agents can support human planners, ease their cognitive burden by giving advice on the correct use of policies and catch possible violations. The experiments show that agents can effectively prevent policy violations with no significant extra cost.

Multicast Key Management without Rekeying Processes

Lin, I.-C., Tang, S.-S., Wang, C.-M. — Fri, 19 Jun 2009 07:02:21 PDT

Secure multicast provides efficient delivery which includes an identical data from a source to multiple receivers. A common solution is to apply a symmetric key that is used to encrypt the transmitted data. However, the heavy cost of the rekeying process is the main problem in large and dynamic multicast groups. The tree-based architecture is widely used to reduce the rekeying cost in terms of storage, transmission and computation. However, it usually requires extra overhead to keep key tree balance which is in order to achieve logarithmic rekeying cost. In this paper, we shall propose a new RSA-like multicast key management scheme to solve the rekeying problem. Our protocol applies a star-based architecture to eliminate the rekeying processes and provide the good performance when the membership changes in a multicast group. Furthermore, we also provide an extended multicast scheme, in which we combine public-key and symmetric-key cryptosystems to enhance the performance of multicast encryption.

Time-Space Opportunistic Routing in Wireless Ad hoc Networks: Algorithms and Performance Optimization by Stochastic Geometry

Baccelli, F., Blaszczyszyn, B., Muhlethaler, P. — Fri, 12 Jun 2009 08:16:40 PDT

This paper is meant to be an illustration of the use of stochastic geometry for analyzing the performance of routing in large wireless ad hoc (mobile or mesh) networks. In classical routing strategies used in such networks, packets are transmitted on a pre-defined route that is usually obtained by a shortest-path routing protocol. In this paper we review some recent ideas concerning a new routing technique which is opportunistic in the sense that each packet at each hop on its (specific) route from an origin to a destination takes advantage of the actual pattern of nodes that captured its recent (re)transmission in order to choose the next relay. The paper focuses both on the distributed algorithms allowing such a routing technique to work and on the evaluation of the gain in performance it brings compared to classical mechanisms. On the algorithmic side, we show that it is possible to implement this opportunistic technique in such a way that the current transmitter of a given packet does not need to know its next relay a priori, but the nodes that capture this transmission (if any) perform a self-selection procedure to choose the packet relay node and acknowledge the transmitter. We also show that this routing technique works well with various medium access protocols (such as Aloha, CSMA, TDMA). Finally, we show that the above relay self-selection procedure can be optimized in the sense that it is the node that optimizes some given utility criterion (e.g. minimize the remaining distance to the final destination), which is chosen as the relay. The performance evaluation part is based on stochastic geometry and combines simulation as analytical models. The main result is that such opportunistic schemes very significantly outperform classical routing schemes when properly optimized and provided at least a small number of nodes in the network know their geographical positions exactly.

Side-Channel Attack Using Meet-in-the-Middle Technique

Kim, J., Hong, S. — Wed, 10 Jun 2009 09:15:00 PDT

In this paper, we introduce a new side-channel attack using block cipher cryptanalysis named a meet-in-the-middle attack. Using our new side-channel technique we show that advanced encryption standard (AES) with reduced 10 masked rounds is broken, which is faster than the exhaustive key search attack. This implies that one has to mask the entire rounds of the 12-round 192-bit key AES to prevent our attacks. Our result is the first one to analyse AES with reduced 10 masked rounds, while the previous best known side-channel attack is on AES with reduced eight masked rounds.

Fine-Grain Register Allocation and Instruction Scheduling in a Reference Flow

Kim, D.-H., Lee, H.-J. — Tue, 09 Jun 2009 06:40:34 PDT

This paper proposes a new register allocation technique in which register allocation is performed at every reference of a variable. For each reference, the costs of various possible register allocations are estimated by tracing a possible instruction sequence. A cost model is formulated to reduce the scope of tracing. With an extension of the cost model to the estimation of instruction execution time, a new technique for the integration of instruction scheduling and register allocation is also proposed. Experiments show that the proposed register allocation and the integration techniques achieve significant improvements when compared with widely used existing techniques.

The Cognitive Packet Network: A Survey

Sakellari, G. — Fri, 05 Jun 2009 00:28:22 PDT

Current and future multimedia networks require connections under specific quality of service (QoS) constraints which can no longer be provided by the best-effort Internet. Therefore, ‘smarter’ networks have been proposed in order to cover this need. The cognitive packet network (CPN) is a routing protocol that provides QoS-driven routing and performs self-improvement in a distributed manner, by learning from the experience of special packets, which gather on-line QoS measurements and discover new routes. The CPN was first introduced in 1999 and has been used in several applications since then. Here we provide a comprehensive survey of its variations, applications and experimental performance evaluations.

Dynamic Service Execution in Sensor Networks

Thu, 28 May 2009 04:08:44 PDT

Sensor networks face a number of challenges when deployed in unpredictable environments under dynamic, quickly changeable demands, and when shared by many partners, which is often the case in military and security applications. To partially address these challenges, we present a novel target tracking algorithm that can be deployed on various sensor nodes and invoked dynamically when needed by the presence of targets. We also demonstrate that an auction-based mechanism can be used to provide efficient and localized wireless sensor network congestion management for bursty traffic of abstract services based just on user-assigned priorities to different services and the quality of information provided by the services. We present results from using this auction mechanism to resolve congestion caused by packets from competing target tracking missions.

Secure Testable S-box Architecture for Cryptographic Hardware Implementation

Rahaman, H., Mathew, J., Pradhan, D.K. — Wed, 27 May 2009 04:16:40 PDT

It has been recently shown that observability of design for testability techniques compromises cryptographic hardware implementation security in a straightforward manner. During test, the chip can be configured so that it is possible to observe temporal data resulting from the encryption process of a plaintext that eventually exposes the secret key. To this end, we propose a C-testable S-box implementation which is one of the most complex blocks in advanced encryption standard hardware implementation. We divide the S-box structure into a positive polarity Reed–Muller form and tested independently using a BIST circuit. The proposed structure does not use any scan chain for testability, hence avoiding the vulnerability of the chip during testing. Only 14 constant vectors are sufficient to achieve 100% fault coverage in the S-box. The C-testable feature comes with an extra hardware overhead of 15 per cent. By introducing an on-chip testing feature one can avoid potential paths for introducing unwanted access into the on-chip security blocks.

Probabilistic Approaches to Estimating the Quality of Information in Military Sensor Networks

Gillies, D., Thornley, D., Bisdikian, C. — Wed, 20 May 2009 07:21:16 PDT

Modelling based on probabilistic inference can be used to estimate the quality of information delivered by a military sensor network. Different modelling tools have complementary characteristics that can be leveraged to create an accurate model open to intuitive and efficient querying. In particular, stochastic process models can be used to abstract away from the physical reality by describing it as components that exist in discrete states with probabilistically invoked actions that change the state. The quality of information may be assessed by using the model to compute the probability that reports made by the network to its users are correct. In contrast, dynamic Bayesian network models, which have been used in a variety of military applications, are a more suitable vehicle for understanding the overall network performance and making inferences about the quality of information. Queries can be made simply by instantiating some variables and computing the probability distributions over others. We show that it is possible to combine both modelling tools by constructing a Bayesian network over the state variables of the process algebra model. The sparsity of the resulting Bayesian network allows fast propagation of probabilities, and hence interactive querying for the quality of information.

Distributed Hash Table-Based Interrogating-Call Session Control Function Network in the Internet Protocol Multimedia Subsystem for Efficient Query Services

Huang, C.-M., Li, J.-W., Chen, C.-T. — Wed, 20 May 2009 07:21:15 PDT

Internet protocol multimedia subsystem (IMS) is an overlaid infrastructure above the packet-switched domain of the universal mobile telecommunication system core network. IMS enables and enhances real-time multimedia mobile services. IMS signaling and media are separated in IMS. For media session negotiation, two basic procedures in IMS are (i) IMS registration procedure and (ii) IMS incoming call setup procedure. IMS signaling needs to traverse a set of call session control functions (CSCFs), which are proxy-CSCF, interrogating-CSCF (I-CSCF) and serving-CSCF (S-CSCF). However, we observe that I-CSCFs need to query the home subscriber server (HSS) to obtain the name of S-CSCF for each subscriber's request in both the basic procedures. It results in a certain load occuring in the HSS and a certain procedure delay also occurs. Therefore, we employ the distributed hash table (DHT) into IMS to form a DHT-based I-CSCF network. Each I-CSCF in the DHT-based I-CSCF network can share and relieve HSS's load. As a result, the incoming call setup procedure can be speeded up. We also propose two maintaining procedures to maintain the DHT-based I-CSCF network for I-CSCFs join and leave scenarios. We propose one maintaining mechanism to guarantee the proposed system to be able to work well in the failure scenario of I-CSCF. According to the performance evaluation results, the load of HSS is reduced and shared among I-CSCFs in the home network and the signaling delay cost of the incoming call setup procedure is less than that of existent systems even if failure occurs and then is removed.

A Logical Approach to Home Healthcare with Intelligent Sensor-Network Support

Bisiani, R., Merico, D., Mileo, A., Pinardi, S. — Thu, 14 May 2009 00:55:13 PDT

This paper describes an intelligent home healthcare system characterized by a wireless sensor network (WSN) and a reasoning component. The aim of the system is to allow constant and unobtrusive monitoring of a patient in order to enhance autonomy and increase quality of life. Data collected by the sensor network are used to support a reasoning component, which is based on answer set programming (ASP), in performing three main reasoning tasks: (i) continuous contextualization of the physical, mental and social state of a patient, (ii) prediction of possibly risky situations and (iii) identification of plausible causes for the worsening of a patient's health. Starting from different data sources (sensor data, test results, inference results) the reasoning component applies expressive logic rules aimed at correct interpretation of incomplete or inconsistent contextual information, and evaluates correlation rules expressed by clinicians. The expressive power of ASP allows efficient enough reasoning to support prevention, while declarativity simplifies rule-specification and allows automatic encoding of knowledge. Preliminary evaluations show that the combination of an ASP-based reasoning component and a WSN is a good solution for creating a home-based healthcare system.

Imprecision-Tolerant Location Management for Object-Tracking Wireless Sensor Network

Lin, C.-Y., Tseng, Y.-C., Liu, Y.-C. — Sun, 10 May 2009 22:29:12 PDT

An important issue of wireless sensor networks is object tracking, where the key steps include event detection, target classification, location estimation and location management. The main theme of this paper is location management. Because imprecision is an inherent property in object-tracking sensor networks, this paper focuses on the scenarios where users can tolerate a certain degree of imprecision in their query results. We intend to develop a location management scheme that can achieve two goals. First, multiple precision levels are provided. Second, the query cost is proportional to the precision level. To achieve these two goals, we propose a tree-based imprecision-tolerant location management scheme that includes three major components: (1) update and query mechanisms that can support imprecision-tolerant queries, (2) the approach to taking the statistics of imprecision-tolerant queries and (3) a tree construction algorithm that can reduce the query cost and minimize the increment of update cost. Performance evaluations are conducted through simulations to verify the proposed scheme.

Resource-Aware Multimedia Content Delivery: A Gambling Approach

Allani, M., Garbinato, B., Pedone, F. — Sat, 09 May 2009 08:04:42 PDT

In this paper, we propose a resource-aware solution to achieving reliable and scalable stream diffusion in a probabilistic model, i.e. where communication links and processes are subject to message losses and crashes, respectively. Our solution is resource-aware in the sense that it limits the memory consumption, by strictly scoping the knowledge each process has about the system, and the bandwidth available to each process, by assigning a fixed quota of messages to each process. We describe our approach as gambling in the sense that it consists in accepting to give up on a few processes sometimes, in the hope of better serving all processes most of the time. That is, our solution deliberately takes the risk not to reach some processes in some executions, in order to reach every process in most executions. The underlying stream diffusion algorithm is based on a tree-construction technique that dynamically distributes the load of forwarding stream packets among processes, based on their respective available bandwidths. Simulations show that this approach pays off when compared to traditional gossiping, when the latter faces identical bandwidth constraints.

A Categorization Framework for Common Computer Vulnerabilities and Exposures

Chen, Z., Zhang, Y., Chen, Z. — Thu, 07 May 2009 04:51:28 PDT

The dictionary of common vulnerabilities and exposures (CVEs) is a compilation of known security loopholes whose objective is to both facilitate the exchange of security-related information and expedite vulnerability analysis of computer systems. Its lack of categorization and generalization capability renders the dictionary ineffective when it comes to developing defense strategies for clustered vulnerabilities instead of individual exploits. To address this issue, we propose a CVE categorization framework termed CVE Classifier that transforms the dictionary into a classifier that not only categorizes CVEs with respect to diverse taxonomic features but can also evaluate general trends in the evolution of vulnerabilities. With the help of support vector machines, CVE Classifier builds learning models for taxonomic features based on training data automatically extracted from pertinent vulnerability databases including BID, X-Force and Secunia, and CVE entries containing telltale keywords unique to taxonomic features. We use word-stemming and stopword-removal techniques to reduce the dimensions of the feature space formed by CVEs and develop a data fusion and cleansing process to eliminate data inconsistencies to improve classification performance. The CVE classification produced by the proposed framework reveals that the majority of the Internet security loopholes are harbored by a small set of services. Moreover, it becomes evident that the widespread deployment of security devices provides many additional attack points as such devices demonstrate a great mount of vulnerabilities. Finally, the CVE Classifier points out that remotely exploitable security loopholes continue to dominate the CVEs landscape.

A Simulation Model Supporting Time and Non-time Metrics for Web Service Composition

Wu, Z., Xiong, N., Park, J. H., Kim, T.-H., Yuan, L. — Wed, 06 May 2009 03:39:31 PDT

A next generation network (NGN) exploits advanced multiple broadband, quality of service (QoS)-enabled service technologies. The NGN is aimed at users and service-related functions, including web services. Recently, web service composition (WSC) has become a new approach for overcoming many difficult problems confronted by B2B e-commerce, inter-organization workflow management, enterprise application integration etc. Due to the uncertainty of the NGNs and various web services, the performance of the WSC cannot be ensured. How to model it and predict its performance becomes a difficult problem for WSC. In this paper, we propose a novel performance simulation model for WSC, called STPM⁺. The STPM⁺ model can support modeling and simulating the time and non-time QoS metrics. Based on the stochastic timed colored Petri net, the STPM⁺ model can simulate and predict multiple QoS metrics, such as cost, reliability, reputation and so on. To examine the validation of our STPM⁺ model, we have designed and realized a visual performance simulation tool, called VisualWSCPE. Based on VisualWSCPE, we have fulfilled some simulation experiments. The experiment results demonstrate the feasibility and efficiency of the STPM⁺ model.

The Random Neural Network: A Survey

Timotheou, S. — Tue, 05 May 2009 03:47:09 PDT

The random neural network (RNN) is a recurrent neural network model inspired by the spiking behaviour of biological neuronal networks. Contrary to most artificial neural network models, neurons in the RNN interact by probabilistically exchanging excitatory and inhibitory spiking signals. The model is described by analytical equations, has a low complexity supervised learning algorithm and is a universal approximator for bounded continuous functions. The RNN has been applied in a variety of areas including pattern recognition, classification, image processing, combinatorial optimization and communication systems. It has also inspired research activity in modelling interacting entities in various systems such as queueing and gene regulatory networks. This paper presents a review of the theory, extension models, learning algorithms and applications of the RNN.

A Cascadable Random Neural Network Chip with Reconfigurable Topology

Badaroglu, M., Halici, U., Aybay, I., Cerkez, C. — Mon, 04 May 2009 04:27:53 PDT

A digital integrated circuit (IC) is realized using the random neural network (RNN) model introduced by Gelenbe. The RNN IC employs both configurable routing and random signaling. In this paper we present the networking/routing aspects as well as the performance results of an RNN network implemented by the RNN IC. In the RNN model, each neuron accumulates arriving signals and can fire if its potential at a given instant of time is strictly positive. Firing occurs at random, the intervals between successive firing instants following an exponential distribution of constant rate. When a neuron fires, it routes the generated pulses to the output lines in accordance with the connection probabilities. The number of neurons in the network is programmable and could be connected to each other with any desired neuron interconnection and this connection could be changed on the fly. The RNN chip architecture is cascadable to generate any network topology. All the parts of the RNN circuit are implemented using a standard digital Complimentary-Metal-Oxide-Semiconductor (CMOS) process.

An Efficient Lossless Compression Algorithm for Tiny Nodes of Monitoring Wireless Sensor Networks

Marcelloni, F., Vecchio, M. — Thu, 30 Apr 2009 08:39:50 PDT

Energy is a primary constraint in the design and deployment of wireless sensor networks (WSNs), since sensor nodes are typically powered by batteries with a limited capacity. Energy efficiency is generally achieved by reducing radio communication, for instance, limiting transmission/reception of data. Data compression can be a valuable tool in this direction. The limited resources available in a sensor node demand, however, the development of specifically designed compression algorithms. In this paper, we propose a simple lossless entropy compression (LEC) algorithm which can be implemented in a few lines of code, requires very low computational power, compresses data on the fly and uses a very small dictionary whose size is determined by the resolution of the analog-to-digital converter. We have evaluated the effectiveness of LEC by compressing four temperature and relative humidity data sets collected by real WSNs, and solar radiation, seismic and ECG data sets. We have obtained compression ratios up to 70.81% and 62.08% for temperature and relative humidity data sets, respectively, and of the order of 70% for the other data sets. Then, we have shown that LEC outperforms two specifically designed compression algorithms for WSNs. Finally, we have compared LEC with gzip, bzip2, rar, classical Huffman and arithmetic encodings.

Program Analysis Probably Counts

Di Pierro, A., Hankin, C., Wiklicky, H. — Mon, 27 Apr 2009 06:52:23 PDT

Semantics-based program analysis uses an abstract semantics of programs/systems to statically determine run-time properties. Classic examples from compiler technology include analyses to support constant propagation and constant folding transformations and estimation of pointer values to prevent buffer overruns. More recent examples include the estimation of information flows (to enforce security constraints) and estimation of non-functional properties such as timing (to determine worst case execution times in hard real-time applications). The classical approaches are based on semantics involving discrete mathematics. Paralleling trends in model-checking, there have been recent moves towards using probabilistic and quantitative methods in program analysis. In this paper we start by reviewing both classical and probabilistic/quantitative approaches to program analysis. We shall provide a comparison of the two approaches. We shall use a simple information flow analysis to exemplify the classical approach. The existence of covert information flows through timing channels are difficult to detect using classical techniques; we show how such problems can be addressed using probabilistic techniques.

An Abstract Interpretation Approach for Enhancing the Java Bytecode Verifier

Barbuti, R., De Francesco, N., Tesei, L. — Thu, 23 Apr 2009 19:49:29 PDT

The Java virtual machine embodies a verifier that performs a set of checks on Java bytecode programs before their execution. The verifier carries out an efficient data-flow analysis applied to a type-level abstract interpretation of the code. The implementations of the bytecode verifier presented a significant problem with programs compiled with the Sun Java compiler (until version 1.4.1): there were legal Java programs which were correctly compiled into a bytecode that was rejected by the verifier. The problem was fixed by removing, in version 1.4.2 and following, some interesting features in the compilation of the try-finally Java construct. Because removing such features has a cost in terms of memory space, in this paper we propose to enhance the bytecode verifier to accept such programs, maintaining the space efficiency of the previous versions of the compiler. We define an abstract interpretation framework in which we model the enhanced version of the verifier. The defined abstract interpretation framework can be considered a good basis for other static analyses of bytecode programs.

Modelling Bidders in Sequential Automated Auctions

Velan, K. — Tue, 21 Apr 2009 07:42:33 PDT

Auctions are mechanisms that formalize the rules with which automated trading schemes can be conducted, and in this paper we model the interaction of bidder and seller agents in sequential computerized auctions. We study the outcome of strategies that a designated ‘special bidder’ (SB) may follow in the presence of a collection of other bidders in an English auction, under the assumption that the SB can make bids based on its observation of the ongoing auction as a collective system. In our model, bidding and sale events are continuous time random processes with discrete state-space, where the state-space represents the current value of the most recent bid. We obtain analytical solutions that allow the evaluation of measures of interest to the SB such as the probability of winning, the savings with respect to the maximum payable price in the event of a win and the expected waiting time to win. We examine the effects of the SB's time to bid, and study how its decisions may be selected so as to optimize the SB's measures of interest.

The Bipancycle-Connectivity and the m-Pancycle-Connectivity of the k-ary n-cube

Fang, J.-F. — Tue, 21 Apr 2009 07:42:33 PDT

The interconnection network considered in this paper is the k-ary n-cube that is an attractive variance of the well-known hypercube. Many interconnection networks that are desirable in both theoretical interests and practical systems, including the ring, torus and hypercube, may be regarded as the subclasses of k-ary n-cubes. In this paper, we investigate the pancycle-connected properties of the k-ary n-cube. We show that the k-ary n-cube is bipancycle-connected for k being even. That is, each pair of vertices x and y is contained by a cycle of each even length ranging from the length of the smallest even cycle that contains x and y to N, where N is the order of the network. We also show that the k-ary n-cube is strictly m-pancycle-connected for k being odd and n ≥ 2, where m = nk - n. That is, each pair of vertices is contained by a cycle of each length ranging from nk - n to N; and nk - n has reached the lower bound of the problem.

Special Issue on Artificial Societies for Ambient Intelligence Editorial Introduction

Sadri, F., Stathis, K. — Mon, 20 Apr 2009 06:13:43 PDT

Verifying a Synthesized Implementation of IEEE-754 Floating-Point Exponential Function using HOL

Akbarpour, B., Abdel-Hamid, A. T., Tahar, S., Harrison, J. — Fri, 10 Apr 2009 05:04:24 PDT

Deep datapath and algorithm complexity have made the verification of floating-point units a very hard task. Most simulation and reachability analysis verification tools fail to verify a circuit with a deep datapath like most industrial floating-point units. Theorem proving, however, offers a better solution to handle such verification. In this paper, we have hierarchically formalized and verified a hardware implementation of the IEEE-754 table-driven floating-point exponential function algorithm using the higher-order logic (HOL) theorem prover. The high ability of abstraction in the HOL verification system allows its use for the verification task over the whole design path of the circuit, starting from gate-level implementation of the circuit up to a high-level mathematical specification.

Principles of Model Checking

Laroussinie, F. — Thu, 09 Apr 2009 03:15:29 PDT

A Multicast Routing Scheme for a Universal Spiking Neural Network Architecture

Wu, J., Furber, S. — Wed, 08 Apr 2009 04:08:02 PDT

A multicast routing infrastructure is proposed as a core feature of SpiNNaker, a massively parallel computer for the real-time simulation of large-scale spiking neural networks. The infrastructure is implemented using a communications router, based on an event-driven routing scheme, on each multicore processing node in the system. The design considerations emphasize the difference between the requirements of neural network communications and those of conventional computer networks and on-chip networks. The focus of the design is on neural modelling flexibility, power-efficiency, fault-tolerance and the communication throughput of the router.

Compiling C-like Languages to FPGA Hardware: Some Novel Approaches Targeting Data Memory Organization

Liu, Q., Constantinides, G. A., Masselos, K., Cheung, P. Y.K. — Wed, 08 Apr 2009 04:08:02 PDT

This paper describes our approaches to raise the level of abstraction at which hardware suitable for accelerating computationally intensive applications can be specified. Field-programmable gate arrays are becoming adopted as a computational platform by the high-performance computing community, but there are challenges to extract maximum performance from these devices. Unlike other approaches, our focus is on data memory organization and input–output bandwidth considerations, which are the typical stumbling block of existing hardware compilation schemes. We describe our approaches, which are based on formal optimization techniques, and present some results showing the advantage of exposing the interaction between data memory system design and parallelism extraction to the compiler.

Turning Back Time--What Impact on Performance?

Harrison, P. G. — Sat, 04 Apr 2009 05:45:44 PDT

Consistent with the divide-and-conquer approach to problem solving, a recursive result is presented in the domain of stochastic modelling that derives product-form solutions for the steady state probabilities of certain networks composed from interacting Markov chains. Practical applications include multi-tasking operating systems, communication channels and multi-tiered storage systems. The approach is also applied to the computation of response time quantiles, which are vital in transaction processing, computer communication service level agreements and other operational systems. The joint probability distribution of the sojourn times of a tagged task at each node in a network is determined by noting that this is the same in both the forward and reversed processes. In this way, existing results for response time probability densities in tandem, tree-like, and overtake-free Markovian queueing networks are quickly and systematically obtained. We further show how to apply the method in more general networks.

Discussants' Comments on the Computer Journal Lecture by Peter Harrison presented at the British Computer Society on 24th February 2009

Gelenbe, E., Gilmore, S. — Wed, 01 Apr 2009 05:52:09 PDT

Dynamic Neighbourhood Cellular Automata

Dantchev, S. — Sat, 28 Mar 2009 05:41:36 PDT

We propose a definition of cellular automaton in which each cell can change its neighbourhood during a computation. This is done locally by looking not farther than neighbours of neighbours and the number of links remains bounded by a constant throughout. We suggest that dynamic neighbourhood cellular automata can serve as a theoretical model in studying algorithmic and computational complexity issues of ubiquitous computations. We illustrate our approach by giving an optimal, logarithmic time solution of the Firing Squad Synchronization problem in this setting.

Convivial Ambient Technologies: Requirements, Ontology and Design

Caire, P., van der Torre, L. — Tue, 17 Mar 2009 06:09:45 PDT

In this paper we discuss the use of the social concept ‘conviviality’ for computer science in general, and for the development of ambient technologies in particular. First, we give a survey of the use of the concept ‘conviviality’ in the social sciences. Conviviality is usually considered a positive concept related to sociability. However, further analysis reveals a negative side related to lack of diversity, privacy and ethical issues. Second, we argue that conviviality requirements for ambient intelligence are challenging, because ambient technologies give rise to a new virtual and social reality, and conviviality issues play a central role in applications that are concerned with the interaction of material, virtual and social realities. Conviviality highlights an important challenge that we illustrate with examples that emphasize ethical issues, such as privacy threats, surveillance of users and identity theft. Intelligent interfaces, for example, allow instant interactions and thereby create strong needs for coordination and regulation mechanisms that have to be addressed to ensure the safeguard of individuals against abuses, such as privacy intrusions and identity manipulations. Third, we propose a conviviality ontology by operationalizing the fuzzy concept of ‘conviviality,’ such that it can be used in computer science in the same way as other social concepts such as ‘service,’ ‘contract’ or ‘trust’ are used in this area. Conviviality is defined using dependence networks, and tools for conviviality are based on, what we call, conviviality masks. Fourth, we illustrate how convivial ambient intelligence applications can be designed using our operationalized concept of conviviality. We illustrate our arguments and contributions with a running example on the use of ambient technologies in digital cities, as a prototypical example where material reality such as ambient technologies interacts with virtual and social realities.

Introduction to Software Testing

Majumdar, R. — Fri, 13 Mar 2009 01:00:09 PDT

Ambient Intelligence for Supporting Task Continuity across Multiple Devices and Implementation Languages

Paterno, F., Santoro, C., Scorcia, A. — Fri, 13 Mar 2009 01:00:08 PDT

Nowadays users are surrounded by environments characterized by an abundance of devices and appliances that they use for carrying out their everyday activities. In order to improve user experience, the surrounding environments should be intelligent enough to allow users to freely move around and be able to perform their tasks in a continuous manner, without forcing them to start their interactive session from scratch at each device change. In this paper, we present an agent-based solution able to support migration of interactive applications among various devices, including digital TVs and mobile devices, and therefore useful for users freely moving about in the home and outdoor. The aim is to provide users with a seamless and supportive environment for ubiquitous access in multi-device contexts of use. The proposed open architecture for migratory user interfaces (UIs) is composed of several agents. It exploits their functionalities and is able to automatically build logical descriptions of existing interactive Web applications and then dynamically generate UIs that are adapted to various types of target devices and implementation languages, including non-Web languages, with the state updated to the point at which it was left off in the previous device.

Data Mining: A Knowledge Discovery Approach

Gazi, B. — Fri, 13 Mar 2009 01:00:07 PDT

Loopless Generation of Non-regular Trees with a Prescribed Branching Sequence

Wu, R.-Y., Chang, J.-M., Wang, Y.-L. — Wed, 11 Mar 2009 06:49:30 PDT

An ordered tree is called a non-regular tree with a prescribed branching sequence (or non-regular tree for short) if its internal nodes have a prespecified degree sequence in preorder list. We define a concise representation, called right distance sequences to describe such trees. A coding tree helps us to systematically investigate the structural representation of non-regular trees. Consequently, we present a loopless algorithm to generate Gray-codes of non-regular trees using right distance sequences.

A Context-Aware Similarity Search for a Handwritten Digit Image Database

Cha, G.-H. — Sat, 28 Feb 2009 05:43:50 PST

In this paper, we propose a context-aware similarity search algorithm for a handwritten digit image database. Though we apply our algorithm to the search of handwritten digit images, the devised technique is generally applicable to other types of content-based image retrieval (CBIR). One of the central problems regarding CBIR is the semantic gap between the low-level features computed automatically from images and the human interpretation of image content. Many search algorithms that are used in CBIR have used the Minkowski metric (or L_p-norm) to measure similarity between image pairs. However those functions cannot adequately capture the aspects of the characteristics of the human visual system as well as the nonlinear relationships in contextual information given by images in a collection. Our new search algorithm tackles this problem by employing a new similarity measure and a ranking strategy that reflect the nonlinearity of human perception and contextual information in an image collection. Our search algorithm yields superior experimental results on a real handwritten digit image database and demonstrates its effectiveness.

Using the Relational Model to Capture Topological Information of Spaces

Bradley, P. E., Paul, N. — Fri, 27 Feb 2009 08:15:54 PST

Motivated by research on how topology may be a helpful foundation for building information modelling, a relational database version of the notions of chain complex and chain complex morphism is defined and used for storing cw-complexes and their morphisms, hence instances of building projects and different views upon them, into relational databases. In many cases, this can be done without loss of topological information. The equivalence of categories between sets with binary relations and Alexandrov spaces is proven and used to incorporate the relational complexes into the more general setting of topological databases. For the latter, a topological version of a relational query language is defined by transferring the usual relational algebra operators into topological constructions. In the end, it is proven that such a topological version of relational algebra in general must be able to compute the transitive closure of a relation.

Efficient Semantic Information Exchange for Ambient Intelligence

van Diggelen, J., Beun, R.-J., van Eijk, R. M., Werkhoven, P. J. — Thu, 26 Feb 2009 03:37:00 PST

This paper studies semantic efficiency measures for ambient intelligence. We follow an agent-based approach and investigate how large quantities of information can be efficiently handled. We will show how to dynamically set up a communication network between agents, which aims to minimize the communication load. The approach is based on a formal ontological notion of informativeness, on quantitative measures such as information gain and on the proper use of interaction mechanisms such as Publish/Subscribe. We also present experimental results that were obtained using our prototyping tool called Ubismart.

Modal Logics are Coalgebraic

Cirstea, C., Kurz, A., Pattinson, D., Schroder, L., Venema, Y. — Sat, 21 Feb 2009 02:07:55 PST

Applications of modal logics are abundant in computer science, and a large number of structurally different modal logics have been successfully employed in a diverse spectrum of application contexts. Coalgebraic semantics, on the other hand, provides a uniform and encompassing view on the large variety of specific logics used in particular domains. The coalgebraic approach is generic and compositional: tools and techniques simultaneously apply to a large class of application areas and can, moreover, be combined in a modular way. In particular, this facilitates a pick-and-choose approach to domain-specific formalisms, applicable across the entire scope of application areas, leading to generic software tools that are easier to design, to implement and to maintain. This paper substantiates the authors’ firm belief that the systematic exploitation of the coalgebraic nature of modal logic will not only have impact on the field of modal logic itself but also lead to significant progress in a number of areas within computer science, such as knowledge representation and concurrency/mobility.

Artificial Societies in a Community-Based Approach to Ambient Intelligence

Locatelli, M. P., Loregian, M., Vizzari, G. — Thu, 19 Feb 2009 23:04:33 PST

This paper presents an agent-based approach to the modeling, design and engineering of ambient intelligence systems. The introduced approach balances the management of the complexity related to the enactment of an ambient intelligence scenario between the agents and the structured environment they populate. The dynamics of local actions and interactions of agents situated in this environment originates the overall organized system behaviour. The environment is shaped according to the notion of active coordination artifact, whose seminal definition was given in Computer Supported Cooperative Work literature by Schmidt and Simone and then evolved in other research contexts. A technique to configure and interact with such environments, i.e. the composition of device functionalities according to their high-level features, and services provided, is presented. A scenario is used as an in-depth example, and the architecture of a sample system implementing the same scenario using our reference middleware is discussed.

Effective and Efficient Event Dissemination for RFID Applications

Jin, B., Zhao, X., Long, Z., Qi, F., Yu, S. — Wed, 18 Feb 2009 03:54:07 PST

The adoption of radio frequency identification (RFID) tags and devices facilitates the observation and monitoring of event patterns, while highly temporal restrained RFID data further make events complicated. Although the existing Pub/Sub systems can help distributed applications monitor and disseminate interesting events, they are unable to express RFID-related events directly. Extending a system for new RFID requirements not only needs a lot of work, but also provides no performance guarantees. It is, therefore, necessary to design and implement an effective and efficient Pub/Sub system in order to capture and disseminate RFID-related events. This paper presents a composite subscription specification for RFID-related application scenarios. It enables the subscription of predicates for RFID code as well as various complex events. Moreover, this paper proposes the algorithms for RFID-code subscription matching and complex events detection which have been implemented in our Pub/Sub system, OncePubSub. Also, experiments were conducted to quantify the performance and overhead of the above algorithms. Performance evaluation results indicate that OncePubSub is more efficient than SIENA- and JESS-based systems.

Modeling DNA/RNA Strings Using Resistor--Capacitor (RC) Ladder Networks

Marshall, R. — Tue, 17 Feb 2009 00:07:37 PST

A passive ladder circuit employing resistors and capacitors has been used to model single-stranded DNA/RNA strings. A detailed examination of the circuit's behavior has revealed that a significant number of correspondences may be established between the behavior of such circuits and the biological/chemical properties of DNA/RNA strings. Amino acid classifications such as aromatic/aliphatic, hydrophobic/hydrophilic, alpha-helix former, beta sheet former, n-fold codon redundancy, etc. have been used in making the correspondences. The results of this study have applications in forensics, pharmacogenomics and single-nucleotide polymorphism-based linkage analysis. Also, the electrical model discussed in this paper can be the basis for creating a ‘DNA-chip’ of arbitrarily long genetic sequences using VLSI technology.

General Tree k-Coteries to Reduce the Degradation of Quorums

Kuo, Y.-C. — Tue, 17 Feb 2009 00:07:36 PST

k-Coterie is a useful concept to solve the distributed k-mutual exclusion problem. The distributed k-mutual exclusion algorithms based on k-coteries have benefits of the high fault-tolerance and the low message cost. Harada and Yamashita proposed a basic tree structure to construct tree k-coteries. When the root fails, quorums are degraded and their sizes grow rapidly. In this paper, we propose the general tree structure to construct general tree 1-coteries to reduce the degradation of quorums. In the general tree 1-coterie, the responsibility of the root to construct small quorums could be adjusted. When the root fails, the degradation of quorums could be reduced. Then, we propose the coterie root-join operation to construct general tree k-coteries by root-joining k general tree 1-coteries at a common root. In the general tree k-coterie, the degradation of quorums and the quorum size could be reduced at same time. We show that general tree k-coteries could be complemental. Thus, general tree k-coteries are resilient when the network is 2-partitioned.

B2B Services: Worksheet-Driven Development of Modeling Artifacts and Code

Huemer, C., Liegl, P., Schuster, R., Zapletal, M. — Tue, 17 Feb 2009 00:07:36 PST

In the development process of a B2B system, it is crucial that the business experts are able to express and evaluate agreements and commitments between the partners, and that the software engineers get all necessary information to bind the private process interfaces to the public ones. UN/CEFACT's modeling methodology (UMM) is a Unified Modeling Language (UML) profile for developing B2B processes. The formalisms introduced by UMM's stereotypes facilitate the communication with the software engineers. However, business experts—who usually have a very limited understanding of UML—prefer expressing their thoughts and evaluating the results by plain text descriptions. In this paper, we describe an approach that presents an equivalent of the UMM stereotypes and tagged values in text-based templates called worksheets. This strong alignment allows an integration into a UMM modeling tool and ensures consistency. We show how a specially designed XML-based worksheet definition language allows customization to special needs of certain business domains. Furthermore, we demonstrate how information kept in worksheets may be used for the semi-automatic generation of pattern-based UMM artifacts which are later transformed to web service definition language and business process execution language code.

Reachability Analysis of Augmented Marked Graphs via Integer Linear Programming

Chen, C.-L., Chin, S.-C., Yen, H.-C. — Thu, 12 Feb 2009 05:50:52 PST

Augmented marked graphs (AMGs) are extensions of marked graphs that allow resource sharing. It has been shown that AMGs are useful for modeling and analyzing certain types of flexible manufacturing systems (FMSs). To our knowledge, the techniques developed for analyzing AMGs are mostly based upon checking certain Petri net structures such as siphons. This article exploits the integer linear programming approach for the analysis of a subclass of AMGs called decomposable AMGs. We show that reachability between two configurations of a decomposable AMG can be equated with solving an instance of integer linear programming. We further extend our technique to model checking a type of branching time temporal logics. Examples arisen in FMSs are used to demonstrate the application of our technique.

Slicing Execution with Partial Weakest Precondition for Model Abstraction of C Programs

Yang, X., Wang, J., Yi, X. — Wed, 11 Feb 2009 01:26:44 PST

Model abstraction plays an important role in model checking of source codes of programs. Slicing execution is a lightweight symbolic execution procedure to extract the models of C programs in an over-approximated way. In this paper, we present an approach to improving slicing execution with a novel concept called partial weakest precondition (PWP) to alleviate the space explosion problem. PWPs specify the corresponding weakest precondition conservatively by only considering part of program variables. We present how to integrate PWP with slicing execution, which leads to a compact model with much smaller state space compared with the one obtained by the original slicing execution. A new PWP implementation is also presented to avoid possible exponential PWP formula size and support pointers and aliases as well. The distinguished features of the implementation are that it does not need to translate the program to the passive form beforehand, and it supports loops very well. Comparing with slicing execution without PWP, the experimentation on SSL protocol based on the C source code openssl-0.9.6c shows that the state space may be reduced to only 1/10 after applying PWP.

Mum Effect as an Offshore Outsourcing Risk: A Study of Differences in Perceptions

Sajeev, A.S.M., Ramingwong, S. — Wed, 28 Jan 2009 00:40:12 PST

Mum effect is the risk arising from project members’ reluctance to report negative information. We investigate the cultural factors contributing to this risk in offshore outsourcing. The study was conducted in Thailand with participation from both students and IT professionals. In order to understand the influence of the IT work environment on the risks, we used the student data as a control sample since students and professionals share the same cultural background but only the professionals have the work experience in the IT industry. We use three of Hofstede's cultural characteristics (power distance (PD), long-term orientation and individualism) and three mum effect factors (fear of consequences, communication gap and team solidarity). Our findings show that PD (i.e. inequality based on seniority and other status symbols) has a significant influence on a mum effect factor. Professionals correlate it with team solidarity (Pearson's r = 0.7, p < 0.001) indicating that PD with superiors is likely to influence team members to be protective of each other. There were also significant differences between students’ and professionals’ mean response to PD (t(75) = –2.97, p = 0.004), fear of consequences (t(75) = –3.67, p < 0.001) and communication gap (t(75) = –3.5, p = 0.001), with professionals producing lower mean values, indicating that the work environment within the IT companies is possibly less risky than the general culture.

A Self-Stabilizing O(k)-Time k-Clustering Algorithm

Datta, A. K., Larmore, L. L., Vemula, P. — Sat, 24 Jan 2009 05:51:02 PST

A silent self-stabilizing asynchronous distributed algorithm is given for constructing a k-dominating set, and hence a k-clustering, of a connected network of processes with unique IDs and no designated leader. The algorithm is comparison-based, takes O(k) time and uses O(klog n) space per process, where n is the size of the network. It is known that finding a minimum k-dominating set is NP-hard. A lower bound is given, showing that any comparison-based algorithm for the k-clustering problem that produces clusters of average size more than 2 in the worst case takes (diam) time, where diam is the diameter of the network.

Layered Architecture for Real-Time Sign Recognition

Ibarguren, A., Maurtua, I., Sierra, B. — Thu, 15 Jan 2009 05:03:29 PST

Sign and gesture recognition offers a natural way for human–computer interaction. This article presents a real-time sign recognition architecture including both gesture and movement recognition. Among the different technologies available for sign recognition Data Gloves and accelerometers were chosen for the purposes of this research. Due to the real-time nature of the problem, the proposed approach works in two different tiers, the segmentation tier and the classification tier. In the first stage the glove and accelerometer signals are processed for segmentation purposes, separating the different signs performed by the system user. In the second stage the values received from the segmentation tier are classified. In an effort to emphasize the real use of the architecture, this approach deals specially with problems such as sensor noise and simplification of the training phase.

Some Extensions on Threshold Visual Cryptography Schemes

Liu, F., Wu, C., Lin, X. — Thu, 15 Jan 2009 02:52:29 PST

Droste [CRYPTO’96] proposed a construction of threshold visual cryptography scheme (TVCS) under the visual cryptography model of Naor and Shamir, i.e. the visual cryptography model with the underlying operation OR. In this article, we give three extensions of TVCS. First, we prove that the TVCS proposed by Droste which was based on the OR operation is still a valid TVCS under the XOR operation, and then we propose a method to further reduce its pixel expansion. We then propose an interesting construction of TVCS with all shares being concolorous. Finally, we give a construction of threshold extended visual cryptography scheme (TEVCS) with the underlying operation OR or XOR. All of our schemes can be applied to the visual cryptography model introduced by Tuyls et al. (First Int. Conf. Security in Pervasive Computing 2004, International Patent with Application No.: PCT/IB2003/000261).

Multi-Agent Group Programming Based On Co-evolution

Wenjun, L., Tianjiang, W., Fang, L. — Thu, 15 Jan 2009 02:52:29 PST

As an effective means of multi-agent problem solving, autonomous individual programming and interaction that are essential need, are limited in their ability to accommodate the interests of others, and therefore, may unnecessarily constrain the solving ability and negotiability of an agent, particularly in a distributed cooperative environments founded on private and uncertain information. In this paper, a multi-agent group programming model is presented, where each agent executes local programming by evolutionary search. Based on co-evolution idea, agents resolve conflicts and revise their own search direction to optimize local and social objectives in an interactive process by means of clustering and group choice. Finally, the paper presents simulation results that illustrate the operational effectiveness of our agent group programming model.

Multiparty Contracts: Agreeing and Implementing Interorganizational Processes

van der Aalst, W. M.P., Lohmann, N., Massuthe, P., Stahl, C., Wolf, K. — Thu, 04 Dec 2008 22:24:06 PST

To implement an interorganizational process between different enterprizes, one needs to agree on the ‘rules of engagement’. These can be specified in terms of a contract that describes the overall intended process and the duties of all parties involved. We propose to use such a process-oriented contract which can be seen as the composition of the public views of all participating parties. Based on this contract, each party may locally implement its part of the contract such that the implementation (the private view) agrees on the contract. In this paper, we propose a formal notion for such process-oriented contracts and give a criterion for accordance between a private view and its public view. The public view of a party can be substituted by a private view if and only if the private view accords with the public view. Using the notion of accordance, the overall implemented process is guaranteed to be deadlock-free and it is always possible to terminate properly. In addition, we present a technique for automatically checking our accordance criterion. A case study illustrates how our proposed approach can be used in practice.

Data Mining with Decision Trees: Theory and Applications

Levene, M. — Tue, 02 Dec 2008 20:48:29 PST

A Formal Model of Ontology for Handling Fuzzy Membership and Typicality of Instances

Au Yeung, C.-m., Leung, H.-F. — Mon, 24 Nov 2008 01:48:22 PST

Ontology has become increasingly important in facilitating information exchange, particularly in the context of the Semantic Web. Currently, most existing ontology models can only specify concepts as crisp sets. However, concepts that are without clear boundaries or are vague in meanings are abundant. Existing ontology models are therefore unable to cope with many real cases effectively. In addition, with respect to a certain category, certain objects can be considered as more representative or typical, which are explained by cognitive psychologists using the Prototype Theory of concepts. Based on this theory, we propose a formal model for fuzzy ontologies. This model is equipped with likeliness, the extent to which an object is considered as an instance of a concept, and typicality, the representativeness of an object in a concept. This model enables ontologies to model concepts and bring the results of reasoning closer to human thinking. Our work is based on an in-depth investigation of the limitations of existing models and findings in cognitive psychology. The nature and differences between likeliness and typicality are also thoroughly discussed. In addition, we present a logic for the ontology model which is based on fuzzy propositional modal logic.

Designing Effective Policies for Minimal Agents

Broda, K., Hogger, C. J. — Mon, 24 Nov 2008 22:54:08 PST

A policy for a minimal reactive agent is a set of condition-action rules used to determine its response to perceived environmental stimuli. When the policy pre-disposes the agent to achieving a stipulated goal we call it a teleo-reactive policy. This paper presents a framework for constructing and evaluating teleo-reactive policies for one or more minimal agents, based upon discounted-reward evaluation of policy-restricted subgraphs of complete situation graphs. The main feature of the method is that it exploits explicit associations of the agent's perceptions with states. The framework allows to construct and evaluate policies for a number of cooperating agents by focusing upon the behaviour of a single representative of them. This abstraction ameliorates the potential combinatorial burden. Within the framework varied behaviours can be modelled, including communication between agents. Simulation results presented here indicate that the method affords a good degree of predictive power. The paper presents two different branch and bound algorithms used to optimize policy evaluation.

Design and Implementation of the DLNA Family Intercom System for Smart Homes

Lai, C.-F., Huang, H.-C., Huang, Y.-M., Chao, H.-C. — Thu, 20 Nov 2008 00:41:59 PST

In a traditional intercom system that only allows place-to-place communication in a house, it is necessary to dial the extension number of a specific family member, or dial each extension number individually via the intercom broadcasting, in order to reach the desired person. Additional master stations controlled the intercom system are required, and it is load to maintain the stations for general users. In order to solve these problems, we propose the digital living network alliance (DLNA) compatible family intercom system (DFIS): the architecture to support user mobility. This architecture makes it possible to quickly reach a family member without the knowledge of the extension number that caters to a fixed location. In other words, it will be not necessary to dial the extension number of the location of the desired person. We introduce call control and phone handling under the subject of DFIS architecture and demonstrate that the proposed DLNA family intercom device and DLNA family intercom adaptor can work well.

Processor Design - System-on-Chip Computing for ASICs and FPGAs

Jasinski, R. — Fri, 07 Nov 2008 04:48:26 PST

Optimizing Access Point Allocation Using Genetic Algorithmic Approach for Smart Home Environments

Lee, J.-H., Han, B.-J., Lim, H.-J., Kim, Y.-D., Saxena, N., Chung, T.-M. — Tue, 21 Oct 2008 07:56:42 PDT

In recent years, high-bandwidth and low-cost wireless technologies have emerged as a competitive element, enabling the smart home environment. On the other hand, with the increasing demands for various services, the current access point allocation schemes give rise to significant challenges for a stable connection service, bandwidth and load distribution. In this paper, we present an optimal access point allocation scheme based on genetic algorithm that attempts to optimize multiple parameters, such as bandwidth, and load-balancing requirements. The proposed allocation scheme provides a set of approximately efficient solutions, which allows a wireless user to choose an access point based on its capacity and load balancing, not only regarding its signaling strength or service set identifier. The simulation results are provided to demonstrate the impact of the proposed optimization procedure on overall system performance in terms of connection distribution, load balancing and call dropping probability.

Increasing Service Availability in a Wireless Home Network Environment

Lin, C.-Y., Wang, S.-C., Kuo, S.-Y., Chen, C.-Y. — Tue, 14 Oct 2008 00:33:51 PDT

Service-oriented architecture (SOA) paradigm is an inspiring and evolving concept in the context of IT and business services. Recently, various networked embedded systems are penetrating into our life; the unique characteristics of these systems pose many technological challenges. Specifically, the capabilities to interoperate across home appliances and personal digital devices are critical in a smart home environment. As a consequence, the SOA paradigm is introduced as a basis to enhance the service interoperability. However, the service availability is another important concern. In this paper, we focus on augmenting the smart home environment with high service availability. First, we point out the potential problems by adopting the universal plug and play (UPnP) quality of service (QoS) architecture to deliver services with QoS requirements in wireless home networks. After that, we propose a local detour mechanism to tolerate link congestions and node/link failures. Furthermore, the proposed mechanism is based on standard UPnP actions, so that modifications to the existing UPnP QoS architecture are not required. Compared with content-adaptive and resource-adaptive-based approaches operated on fixed service routing paths, our work not only guarantees content quality, but also tolerates topology changes in wireless home networks.

GA-Based Keyword Selection for the Design of an Intelligent Web Document Search System

Chou, C.-H., Lee, C.-H., Chen, Y.-H. — Tue, 14 Oct 2008 06:53:00 PDT

The main steps for designing an automatic document classification system include feature extraction and classification. In this article a method to improve feature extraction is proposed. In this method, genetic algorithm was applied to determine the threshold values of four criteria for extracting the representative keywords for each class. The purpose of these four threshold values is to extract as few representative keywords as possible. This keyword extraction method was combined with two classification algorithms, vector space model and support vector machine, for examining the performance of the proposed classification system under various extracting conditions.

SH-CRBAC: Integrating Attribute and Status Constraints into the RBAC Model in Smart Home Systems

Zou, D., Park, J. H., Kim, T.-h., Chen, X. — Tue, 14 Oct 2008 06:52:59 PDT

The requirements for access control have been increased significantly in smart home systems. Many factors such as user ID, user location, service usage conditions and so on, regarded as authorization attributes, are important in making authorization decision in smart home systems. We investigate into the dynamic characteristics of the authorization in smart home systems and propose a new access-control model, SH-CRBAC, which aims to combine the advantages of attribute-based authorization mechanism and role-based access-control mechanism, and imposes attribute and status constraints on the RBAC model and enhances the generality and flexibility of authorization significantly in smart home systems. The status consistency of SH-CRBAC is analysed, and we also analyse the characteristics of SH-CRBAC through comparison with other popular existing authorization models in smart home systems.

The Correspondence Analysis Platform for Uncovering Deep Structure in Data and Information

Murtagh, F. — Tue, 09 Sep 2008 09:08:54 PDT

We study two aspects of information semantics: (i) the collection of all relationships, (ii) tracking and spotting anomaly and change. The first is implemented by endowing all relevant information spaces with a Euclidean metric in a common projected space. The second is modelled by an induced ultrametric. A very general way to achieve a Euclidean embedding of different information spaces based on cross-tabulation counts (and from other input data formats) is provided by correspondence analysis. From there, the induced ultrametric that we are particularly interested in takes a sequential—e.g. temporal—ordering of the data into account. We employ such a perspective to look at narrative, ‘the flow of thought and the flow of language’ (Chafe). In application to policy decision making, we show how we can focus analysis in a small number of dimensions.

Near-Optimal Tracking for Residents' Comfort in Context-Aware Heterogeneous Smart Environments

Saxena, N., Roy, A., Shin, J. — Fri, 22 Aug 2008 08:05:25 PDT

An information-theoretic, optimal framework is developed for tracking the residents in a context-aware heterogeneous smart environment. The framework envisions that each individual sensor system operates fairly independently and does not require public knowledge of individual topologies. The resident-tracking problem is formulated in terms of a new concept of weighted entropy. The framework is truly universal and provides an optimal, online learning and prediction of inhabitant's movement (location) profiles from the symbolic domain. The overall optimal tracking in heterogeneous smart homes is proved to be an NP-complete problem, and a greedy heuristic for near-optimal tracking is proposed. The concept of asymptotic equipartition property is also explored to predict the inhabitant's most likely path segments (comprising coverage areas of different sensor systems) with very good accuracy. Successful prediction helps in on-demand operations of automated indoor devices along the inhabitant's future paths and locations, thus providing the necessary comfort at a near-optimal cost. Simulation results on a typical smart home corroborate a high prediction success of ~91%, thereby providing sufficient resident-comfort (≥7 in the scale of 10) while reducing the daily energy consumption and manual operations to less than one-third of its original values.

Ambient Ecologies in Smart Homes

Goumopoulos, C., Kameas, A. — Thu, 21 Aug 2008 08:20:45 PDT

An important characteristic of ubiquitous computing (UbiComp) environments is the integration of information, communication and sensing technologies into our everyday objects, giving rise to a new proactive computing model in homes. A smart home uses networked sensors, devices and appliances to build an intelligent environment in which many activities in the home are automated and where devices and services seamlessly cooperate to support domestic tasks. Programming and maintaining such an infrastructure is challenging because suitable abstractions are currently missing. In this work we have attempted to define ambient ecologies as a metaphor for modeling UbiComp applications, specify design patterns and programming principles and develop infrastructure to provide a paradigm of application engineering and tools to support ambient ecology designers, developers and end-users. We describe our model and the middleware architecture and present the engineering of applications in a smart home environment.

Joint Routing and Rate Control Scheme for Multi-Stream High-Definition Video Transmission over Wireless Home Networks

Zhou, L., Zheng, B., Wei, A., Geller, B., Cui, J. — Thu, 21 Aug 2008 01:18:27 PDT

The support for multiple high-definition video streams in wireless home networks requires appropriate routing and rate control measures, ascertaining the reasonable links for transmitting each stream and the rate of the video to be delivered over the chosen links. In this paper, we invest the combination of the routing and rate control in a united convex optimization formulation and propose a distributed joint solution based on cross-layer design. We first develop a distortion model which captures both the impact of encoder quantization and packet loss due to network congestion on the overall video quality. Then, the optimal joint rate control and routing scheme is realized by adapting its rate to the time-varying traffic and minimizing the overall network congestion. Furthermore, simulation results are provided, which demonstrate the effectiveness of our proposed joint routing and rate control scheme in the context of wireless home networks.

An Improved RFID-Based Locating Algorithm by Eliminating Diversity of Active Tags for Indoor Environment

Zhang, T., Chen, Z., Ouyang, Y., Hao, J., Xiong, Z. — Wed, 06 Aug 2008 03:34:53 PDT

The location awareness is a crucial foundation for perceptions of the surroundings in the smart environment. Radio frequency identification (RFID), as one of the most promising technologies, plays a more important role in the indoor location awareness. This paper surveys current RFID-based locating research and discusses the problem that is brought by the tag's diversity derived from different manufacturer types and different used-time of built-in battery. We present the algorithm named RFDiffFreeLoc to improve the location precision by eliminating the dissimilarity among tags. In the stimulation experiments, we analyze the impact of noise on performance and contrast our algorithm with the existing LANDMARC algorithm. The simulation performances show that our algorithm is feasible via two metrics: the mean error and cumulative error distribution. The results indicate that RFDiffFreeLoc significantly increases the locating accuracy: when the space between the reference tags is 1 m, the mean error drops 0.076–0.344 m according to various noise conditions. Furthermore, a prototype system named RFHome is deployed for validating the algorithm in the actual home environment. The practical experimental results demonstrate that our algorithm is more effective than previous LANDMARC algorithm.

Home Network Device Authentication: Device Authentication Framework and Device Certificate Profile

Lee, Y.-K., Lee, D. G., Han, J.-W., Kim, T.-H. — Thu, 24 Jul 2008 04:37:57 PDT

As home devices have various functions and have improved computing power and networking ability, home device authentication has become increasingly important for improving the security of home network users. Moreover, device authentication supplies user convenience for the home network service user because it can replace the user authentication required for the used home network service. In addition, the safety of the home network can be strengthened if device authentication is considered in addition to the authentication and access control for the home network user. In this paper, we describe home device authentication, which is a basic and essential element of home network security. We propose a home device authentication framework, home device registration, method of issuing certificates and a home device certificate profile. Our home device certificate profile is based on the Internet X.509 certificate. In short, our device authentication concept can offer convenience and security to users of a home network service.

Congruence Formats for Weak Readiness Equivalence and Weak Possible Future Equivalence

Huang, X., Jiao, L., Lu, W. — Fri, 18 Apr 2008 21:41:35 PDT

Weak equivalences are important behavioral equivalences in the course of specifying and analyzing reactive systems using process algebraic languages. In this paper, we propose a series of weak equivalences named weak parametric readiness equivalences, which take two previously known behavioral equivalences, i.e. the weak readiness equivalence and the weak possible future equivalence, as their special cases. More importantly, based on the idea of structural operational semantics, a series of rule formats are presented to guarantee congruence for these weak parametric readiness equivalences, i.e. to show that the proposed rule formats can guarantee the congruence of their corresponding weak parametric readiness equivalences. This series of rule formats reflects the differences in the weak parametric readiness equivalences. We conclude that when the weak parametric readiness equivalences become coarser, their corresponding rule formats turn tighter.

Implementation of Learning Path in Process Control Model

Luo, J., Kong, W., Ge, L. — Wed, 26 Mar 2008 04:11:29 PDT

Few e-Learning systems in pervasive environments take learning activities as a part of the learning process and give much flexibility to instructors to define a structural course which is helpful for students to navigate distributed learning resources. In this paper, we propose a process control model in Web-based e-Learning, and illustrate how to implement process control through learning path with workflow technology. This model improves the learning efficiency by providing instructors tools to design courses with learning paths and select the popular learning objects. It also enables students to achieve an orderly learning experience through defined learning path.

A Hierarchy of Behavioral Equivalences in the {pi}-calculus with Noisy Channels

Cao, Y. — Sat, 15 Mar 2008 00:36:52 PDT

The -calculus is a process algebra where agents interact by sending communication links to each other via noiseless communication channels. Taking into account the reality of noisy channels, an extension of the -calculus, called the _N-calculus, has been introduced recently. This paper presents an early transitional semantics of the _N-calculus, which is not a directly translated version of the late semantics of _N, and then extends six kinds of behavioral equivalences consisting of reduction bisimilarity, barbed bisimilarity, barbed equivalence, barbed congruence, bisimilarity and full bisimilarity into the _N-calculus. Such behavioral equivalences are cast in a hierarchy, which is helpful to verify behavioral equivalence of two agents. In particular, this paper shows that due to the noisy nature of channels, the coincidence of bisimilarity and barbed equivalence, as well as the coincidence of full bisimilarity and barbed congruence, in the -calculus does not hold in _N.

Smart-Context: A Context Ontology for Pervasive Mobile Computing

Moore, P., Hu, B., Wan, J. — Tue, 04 Mar 2008 05:05:14 PST

This paper addresses context in intelligent context-aware systems to support personalised service provision and cooperative computing. Context processing, context modelling, ontology, and OWL are introduced and a context reasoning ontology presented. Context implementation reduces to a decision problem which is characterised as one of selecting from a number of potential options based on the relationship between the values that describe the input and the solution, the modelling school of decision analysis attempts to construct an explicit model of such relationships, usually in the form of decision trees. An overview of decision trees with parametric design considerations is presented. Comparisons with related research are drawn and an evaluation and simulation of Smart-Context is presented. RDF/S with OWL and Jena provide an effective basis for autonomous decision making using processing rules, and the issue is one of implementation in adaptable and tractable solutions. A conclusion with open research questions is presented with consideration of potential directions for future research.

Ant-based Energy-aware Disjoint Multipath Routing Algorithm for MANETs

Wu, Z.-Y., Song, H.-T. — Mon, 11 Feb 2008 08:00:27 PST

Ant-based routing protocols for mobile ad hoc networks (MANETs) have been widely explored, but most of them are essentially single-path routing methods that tend to impose a heavy burden on the hosts along the shortest path from source to destination. In this paper, we combine swarm intelligence and node-disjoint multipath routing to alleviate these problems. A novel approach called ant-based energy-aware disjoint multipath routing algorithm (AEADMRA) is proposed. AEADMRA is based on swarm intelligence and especially on the ant colony-based meta heuristic. AEADMRA can discover multiple energy-aware node-disjoint routing paths with a low routing overhead. Simulation results indicate that the performance of AEADMRA outperforms other pertinent algorithms.

A Rule-based Method for Improving Adaptability in Pervasive Systems

Lin, J., Song, C., Wang, H. — Thu, 31 Jan 2008 10:51:53 PST

There are two types of dynamic elements in a pervasive system: the first is where a context varies with shifting environments, and the second is where variables are defined by the dynamic requirements of an application. This makes improving adaptability to dynamic change an important topic in pervasive systems research. Currently, most of the efforts targeting improvements in adaptability focus on context-related issues, other variables being simply encoded in the program directly. This ignores the dynamic complexity of a pervasive system, resulting in poor system adaptability. In this paper, we propose a rule-based method in which the two types of change are separated from the program code. The changes are then stored and processed by means of corresponding rules. In our new method when a change occurs, the system needs only to modify the rules rather than the program code. This makes a pervasive system more robust in its adaptability to dynamic change. Experiments and examples are provided to evaluate the feasibility of the proposed method.

Non-Archimedean Ergodic Theory and Pseudorandom Generators

Anashin, V. — Tue, 22 Jan 2008 07:42:28 PST

The paper develops techniques in order to construct computer programs, pseudorandom number generators (PRNG), that produce uniformly distributed sequences. The paper exploits an approach that treats standard processor instructions (arithmetic and bitwise logical ones) as continuous functions on the space of 2-adic integers. Within this approach, a PRNG is considered as a dynamical system and is studied by means of the non-Archimedean ergodic theory.

Mumford Dendrograms

Bradley, P. E. — Sat, 19 Jan 2008 22:48:39 PST

An effective p-adic encoding of dendrograms is presented through an explicit embedding into the Bruhat–Tits tree for a p-adic number field. This field depends on the number of children of a vertex and is a finite extension of the field of p-adic numbers. It is shown that fixing p-adic representatives of the residue field allows a natural way of encoding strings by identifying a given alphabet with such representatives. A simple p-adic hierarchic classification algorithm is derived for p-adic numbers, and is applied to strings over finite alphabets. Examples of DNA coding are presented and discussed. Finally, new geometric and combinatorial invariants of time series of p-adic dendrograms are developed.

Generalized Distance Functions in the Theory of Computation

Seda, A. K., Hitzler, P. — Thu, 17 Jan 2008 21:51:59 PST

We discuss a number of distance functions encountered in the theory of computation, including metrics, ultra-metrics, quasi-metrics, generalized ultra-metrics, partial metrics, d-ultra-metrics and generalized metrics. We consider their properties, associated fixed-point theorems and some general applications they have within the theory of computation. We consider in detail the applications of generalized distance functions in giving a uniform treatment of several important semantics for logic programs, including acceptable programs and natural generalizations of them, and also the supported model and the stable model in the context of locally stratified extended disjunctive logic programs and databases.

A Policy-Driven Service Composition Method for Adaptation in Pervasive Computing Environment

Zhang, B., Shi, Y., Xiao, X. — Fri, 21 Dec 2007 06:16:58 PST

Service composition allows distributed application, such as multimedia application, to be composed from atomic service units and to adapt dynamically to users' requirements and environment conditions in pervasive computing system. It augments the adaptation action space for the application of pervasive computing. According to the multidimensional QoS (Quality of Service) requirement of pervasive computing system, we proposed a comprehensive service composition method to enhance the capability of application adaptation. First, according to a hierarchy policy model and a policy specification language, strengthened by event calculus, service discovery policy action integrating the situation of user, application, environment and resource can be triggered. Secondly, the proposed physical space model can support the location-aware service discovery and explicit range query to improve the efficiency of the query. To the end, an adaptation policy evaluation model is utilized to maximize an evaluation criterion–quality of satisfaction of users and environment by optimizing the optional service selection and the composition path. Through experiment and discussion of the algorithm, the paper further illustrates the great potential advantage of the solution to service composition.

On Ultrametric Algorithmic Information

Murtagh, F. — Fri, 14 Dec 2007 20:45:18 PST

How best to quantify the information of an object, whether natural or artifact, is a problem of wide interest. A related problem is the computability of an object. We present practical examples of a new way to address this problem. By giving an appropriate representation to our objects, based on a hierarchical coding of information, we exemplify how it is remarkably easy to compute complex objects. Our algorithmic complexity is related to the length of the class of objects, rather than to the length of the object.

Computational Aspects of Monomial Dynamical Systems

Nilsson, M. — Sat, 08 Dec 2007 04:53:32 PST

We consider the dynamics of x ↦ xⁿ, where n ≥ 2 is an integer, over the multiplicative group modulo p^k, where k is a positive integer and p an odd prime. This paper is a review of earlier results by the author, but new results are also contained. Possible applications to pseudorandom number generation will be discussed. The main results are a description of the preperiodic points and an algorithm to find the longest possible cycle. The preperiodic points form trees, all isomorphic as graphs to the preperiodic points of the fixed point 1. When n is a prime, different from p, we can describe the tree structure completely. A formula for the length of the longest cycle is presented. We can find one of the longest cycles of the monomial system using a primitive root modulo p^k as an initial value.

Special Interest Messaging: A Comparison of IGM Approaches

Cutting, D., Quigley, A., Landfeldt, B. — Sun, 02 Dec 2007 18:43:03 PST

Hundreds of technical, special interest Internet weblogs are already generating thousands of niche articles worldwide, and many institutions are starting to create internal blogs for team collaboration. As this style of communication becomes more pervasive in the lives of employees and researchers, the difficulty of finding relevant information only grows with the number of authors and articles. To reduce the load, we propose using implicit group messaging (IGM) to automatically deliver relevant content to readers grouped by shared characteristics or interests. In this paper, we outline a context-aware application suited to special interest messaging and describe three alternative delivery models including our peer-to-peer (P2P) design called SPICE and a broker-based design. We investigate the advantages and disadvantages of each approach through detailed simulations driven by realistic data and actual national/global network topologies. We find that although a broker-based design is generally the most network efficient and lowest latency, a structured P2P system can offer exceptionally low and fair loading across peers and network links without relying on specialized broker nodes.

Detection Of Normal and Novel Behaviours In Ubiquitous Domestic Environments

Rivera-illingworth, F., Callaghan, V., Hagras, H. — Fri, 09 Nov 2007 06:56:37 PST

The importance of ubiquitous environments has increased in recent years as it has been recognized as a paradigm that can improve the quality of life of many sectors of the population especially care of elderly people by providing automated environments that adapt and respond to its inhabitants' needs. The aim of the work presented here is to provide a solution to the problem of recognition and detection of human behaviours inside ubiquitous environments by using a neural-network driven embedded agent working with online, real-time data from a network of unobtrusive low-level sensors. The final objective of this system was to classify a ‘normal’ pattern of activities, and sense deviations from it, which could be employed for home care applications.

Significance Delta Reasoning with p-Adic Neural Networks: Application to Shot Change Detection in Video

Benois-Pineau, J., Khrennikov, A. — Fri, 19 Oct 2007 15:32:31 PDT

A new possibility to extract significant changes is given by the so-called p-adic number system. p-Adic metric as opposed to a conventional Euclidean metric is based on hierarchical encoding of information. p-Adic and more generally ultrametric spaces have been already used for modeling the functioning of cognitive systems for their property of inducing hierarchy in decision-making process. In this paper, we benefit from this property in modeling delta reasoning. Indeed p-adics give a possibility to extract significant information, in particular significant delta-changes and furthermore, to preserve this hierarchical structure in the process of performing various operations on the data. Hence, we can create p-adic neural networks operating on hierarchical strings of information. In this paper, an algorithm of random learning of p-adic neural networks is applied to the problem of detection of changes in streams of video information such as shot boundaries.

p-Adic Modelling of the Genome and the Genetic Code

Dragovich, B., Dragovich, A. — Thu, 18 Oct 2007 04:11:18 PDT

This paper presents the foundations of p-adic modelling in genomics. Considering nucleotides, codons, DNA and RNA sequences, amino acids and proteins as information systems, we have formulated the corresponding p-adic formalisms for their investigations. Each of these systems has its characteristic prime number used for construction of the related information space. Relevance of this approach is illustrated by some examples. In particular, it is shown that degeneration of the genetic code is a p-adic phenomenon. We have also put a forward a hypothesis on the evolution of the genetic code assuming that primitive code was based on single nucleotides and chronologically first four amino acids. This formalism of p-adic genomic information systems can be implemented in computer programs and applied to various concrete cases.