The Computer Journal - Advance Access

Robust Super-Peer-Based P2P File-Sharing Systems

Lin, J.-W., Yang, M.-F. — 2009-07-01

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

2009-06-26

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. — 2009-06-26

Agent Support for Policy-Driven Collaborative Mission Planning

2009-06-24

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. — 2009-06-19

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.

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

Konstantopoulos, T. — 2009-06-12

Discussant of Response to the Computer Journal Lecture by Francois Baccelli

Penrose, M. D. — 2009-06-12

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

Baccelli, F., Blaszczyszyn, B., Muhlethaler, P. — 2009-06-12

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. — 2009-06-10

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. — 2009-06-09

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. — 2009-06-05

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.

Events, Causality and Symmetry

Winskel, G. — 2009-06-05

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.

Dynamic Service Execution in Sensor Networks

2009-05-28

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. — 2009-05-27

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. — 2009-05-20

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. — 2009-05-20

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.

On the Usefulness of Fibonacci Compression Codes

Klein, S. T., Ben-Nissan, M. K. — 2009-05-14

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.

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

Bisiani, R., Merico, D., Mileo, A., Pinardi, S. — 2009-05-14

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.

Analyzing Team Decision-Making in Tactical Scenarios

Sukthankar, G., Sycara, K. — 2009-05-12

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. — 2009-05-12

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

Harn, L., Hsin, W.-J., Lin, C. — 2009-05-11

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.

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

Lin, C.-Y., Tseng, Y.-C., Liu, Y.-C. — 2009-05-10

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. — 2009-05-09

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. — 2009-05-07

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. — 2009-05-06

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. — 2009-05-05

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. — 2009-05-04

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. — 2009-04-30

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. — 2009-04-27

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. — 2009-04-23

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. — 2009-04-21

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. — 2009-04-21

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. — 2009-04-20

A Digest and Pattern Matching-Based Intrusion Detection Engine

Chen, Z., Zhang, Y., Chen, Z., Delis, A. — 2009-04-15

Intrusion detection/prevention systems (IDSs/IPSs) heavily rely on signature databases and pattern matching (PM) techniques to identify network attacks. The engines of such systems often employ traditional PM algorithms to search for telltale patterns in network flows. The observations that real-world network traffic is largely legitimate and that telltales manifested by exploits rarely appear in network streams lead us to the proposal of Fingerprinter. This framework integrates fingerprinting and PM methods to rapidly distinguish well-behaved from malicious traffic. Fingerprinterproduces concise digests or fingerprints for attack signatures during its programming phase. In its querying phase, the framework quickly identifies attack-free connections by transforming input traffic into its fingerprint space and matching its digest against those of attack signatures. If the legitimacy of a stream cannot be determined by fingerprints alone, our framework uses the Boyer–Moore algorithm to ascertain whether attack signatures appear in the stream. To reduce false matches, we resort to multiple fingerprinting techniques including Bloom–Filterand Rabin–Fingerprint. Experimentation with a prototype and a variety of traces has helped us establish that Fingerprintersignificantly accelerates the attack detection process.

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

Akbarpour, B., Abdel-Hamid, A. T., Tahar, S., Harrison, J. — 2009-04-10

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. — 2009-04-09

A Multicast Routing Scheme for a Universal Spiking Neural Network Architecture

Wu, J., Furber, S. — 2009-04-08

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. — 2009-04-08

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. — 2009-04-04

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.

Implications of Electronics Technology Trends for Algorithm Design

Greenfield, D., Moore, S. — 2009-04-02

Scaling of electronics technology has brought us to a pivotal point in the design of computational devices. Technology scaling favours transistors over wires which has led us into an era where communication takes more time and consumes more power than the computation itself. This technology driver inevitably pushes us toward a communication-centric approach to algorithm design. To assess the efficiency of an algorithm we will need to be able to predict data movement both in time and space. We demonstrate that algorithms exhibit fractal like communication behaviour which is likely to help with such an analysis. Moreover, successfully exploiting these fractal properties will allow us to reduce communication, thereby increasing performance and power efficiency.

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

Gelenbe, E., Gilmore, S. — 2009-04-01

Dynamic Neighbourhood Cellular Automata

Dantchev, S. — 2009-03-28

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. — 2009-03-17

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. — 2009-03-13

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

Paterno, F., Santoro, C., Scorcia, A. — 2009-03-13

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. — 2009-03-13

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

Wu, R.-Y., Chang, J.-M., Wang, Y.-L. — 2009-03-11

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.

Special Issue on Profiling Expertise and Behaviour

Mirkin, B., Levene, M. — 2009-03-06

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

Cha, G.-H. — 2009-02-28

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. — 2009-02-27

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. — 2009-02-26

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. — 2009-02-21

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. — 2009-02-19

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. — 2009-02-18

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. — 2009-02-17

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. — 2009-02-17

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. — 2009-02-17

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.

Design and Evaluation of a Distributed Clustering Algorithm for Mobile ad hoc Networks

Lacks, D., Chatterjee, M., Kocak, T. — 2009-02-14

This paper proposes a new clustering algorithm for global positioning system (GPS)-based mobile ad hoc networks that takes into consideration the direction of the overall traffic flow in the network. The proposed cluster leader logic algorithm is motivated by the GPS quorum hybrid routing algorithm, where clusterheads are positioned on the terrain upon a conceptual cellular grid. The proposed distributed clustering algorithm chooses the clusterheads based on the traffic flow patterns, i.e. the nodes best suited to forward and route network traffic are selected. Our approach allows a clusterhead which is overwhelmed with sending packets to identify an additional clusterhead from nodes available in its cell to share its load. Likewise, clusterheads with low load will try to relinquish their role as a clusterhead. We propose a new concept called cell fanning that allows collocated clusterheads in one cell to share routing responsibilities by declaring which cells they are responsible for routing packets to. We conducted extensive simulation experiments with enforced directional traffic patterns. Two important results are presented: power consumption per clusterhead and average queuing delay for each clusterhead. Results in terms of message overheads, number of clusterheads, power consumption, and queuing delay reveal that system performance is enhanced when clusterheads are chosen considering the direction of the traffic flow.

Just-In-Time Cache for Capsule-Based Active Networks

Huang, T.-C., Shieh, C.-K., Miao, Y.-B. — 2009-02-12

Active networking introduces a novel programming paradigm to applications by injecting codes into networks in order to program them. Among the approaches to injecting codes into networks, active networking attracts most research communities to explore the capsule-based active network, where the packet named the capsule can carry codes and data together to customize the processing of the packet in network devices with the codes. Because a capsule has space limitations that harm application developments in capsule-based active networks, the just-in-time cache (JITC) is proposed to alleviate capsule space limitations. The JITC is an innovative idea to introduce a cache into a capsule besides into a network device. The JITC automatically tailors codes to the need of a capsule while processing the capsule in a network device. The JITC allows a capsule merely to carry the necessary codes to traverse active networks and makes a network device download codes on behalf of the capsule on demand. The JITC allows applications to disable the cache, control the cache size, and specify the required cache placement policy in a capsule to achieve the optimal performance. Currently, the JITC supports six canonical cache placement policies. The JITC is implemented in Windows 2000 as a proof of concept. In the experiments, the JITC has trivial overheads in contrast to other common overheads in the existing solutions. The JITC outperforms the existing solutions in throughput, processing delay, resource sensitivity, and bandwidth conservation in the cache-policy-free situation. Besides, the JITC has examples for the six cache placement policies to demonstrate the performance improvement with each of them.

Reachability Analysis of Augmented Marked Graphs via Integer Linear Programming

Chen, C.-L., Chin, S.-C., Yen, H.-C. — 2009-02-12

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.

i-ProSE: Inferring User Profiles in a Scientific Context

Vivacqua, A. S., Oliveira, J., de Souza, J. M. — 2009-02-12

Scientific environments are known for being highly dynamic, subject to rapid evolution and demanding constant renewal and update. Additionally, science is a highly social arena. However, interpersonal collaboration and knowledge flow in scientific environments are usually more restricted. Collaboration is intense among small groups of people working on specific problems within a domain, but low between groups. As user profiling has been extensively used as a basis for recommendation, personalization and matchmaking systems, a better profile identification can improve interaction levels among researchers belonging to the same domain but working in different laboratories. Profiles may be constructed in two ways: either through explicit declaration by the user or through the observation of users’ actions. Many systems employ one approach to the exclusion of the other. We contend that a combined approach will yield better results, especially on scientific scenario, providing a mix of declared and inferred information. In this article, we present inference-based profiles in scientific environments (i-ProSE), an integrated system that dynamically creates and maintains scientific user profiles based both on declared information and on observed behaviour. The i-ProSE can be used to locate experts, deliver content, build communities, find collaborators for long-term projects or detect instantaneous opportunities for informal collaboration, which is presented with a short study case.

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

Yang, X., Wang, J., Yi, X. — 2009-02-11

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. — 2009-01-28

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.

{lambda}_SAOP: A Security AOP Calculus

Alhadidi, D., Belblidia, N., Debbabi, M., Bhattacharya, P. — 2009-01-25

This paper presents an aspect-oriented calculus for security called _SAOP. It is based on the _calculus and contains pointcuts that are relevant to security hardening of applications. The main contribution of the paper is a semantics for _SAOP advice weaving in the presence of these pointcuts. We instrument the effect-based type inference system to inject advices into expressions during static typing. The proposed semantics for advice weaving is in the spirit of AspectJ, a prominent aspect-oriented programming language, where advices are injected before, after or around the join points that match their respective pointcuts. For this purpose, we accommodate the effect-based inference algorithm to take matching and weaving processes into consideration. In addition, we establish the required soundness and preservation proofs.

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

Datta, A. K., Larmore, L. L., Vemula, P. — 2009-01-24

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. — 2009-01-15

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. — 2009-01-15

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. — 2009-01-15

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.

Provably Secure Password-Based Three-Party Key Exchange With Optimal Message Steps

Chien, H.-Y., Wu, T.-C. — 2008-12-24

A password-based three-party encrypted key exchange (3PEKE) is a protocol that enables any pair of two registered clients to establish session keys with the help of a trusted server such that each client shares only one password with the server. This approach greatly improves the scalability of key agreement protocol in distributed environments and provides great user convenience. This article proposes a new password-based 3PEKE scheme that completes its entire job in only a record low four steps, which we prove that it is optimal for password-based 3PEKE protocols. The security of the proposed scheme, as we will detail later, has been proved in the random oracle model.

Multiparty Contracts: Agreeing and Implementing Interorganizational Processes

van der Aalst, W. M.P., Lohmann, N., Massuthe, P., Stahl, C., Wolf, K. — 2008-12-04

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. — 2008-12-02

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

Au Yeung, C.-m., Leung, H.-F. — 2008-11-24

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. — 2008-11-24

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. — 2008-11-20

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.

A Phase-Based Approach for On-Chip Bus Architecture Optimization

Lee, J., Lee, H.-J., Lee, C. — 2008-11-13

As the integration scale of a chip increases, on-chip interconnects suffer from the increased area occupied by a large number of bus signals. To reduce the overhead for communication, this paper formulates a new concept of an on-chip communication approach, called phase-based interconnection, with an example protocol, system-on-chip network protocol (SNP). In the phase-based communication, a small number of signals called phase signals are used to distinguish the types of signals transmitted through the main communication channel. To identify transactions transmitted through the channel, the SNP protocol defines the allowed sequence of phases for each transaction. A theoretical framework provides conditions for a phase-based protocol to allow immediate decoding of transactions. Simulation results show that the bandwidth of SNP is greater than that of a de facto standard bus protocol although SNP has wires only about three-fifths of the standard bus protocol. Although the signal-toggling rate is increased because of the multiplexed transmission of various signals through a single communication channel, simulation results show that the increase is not significant for multimedia applications that frequently transmit burst transfers. The phase omission of SNP helps to reduce the transaction failure rate to 65% while the hardware implementation cost for the support of phase omission is negligible.

Semantic Analysis of Field Sports Video using a Petri-Net of Audio-Visual Concepts

Bai, L., Lao, S., Smeaton, A. F., O'Connor, N. E., Sadlier, D., Sinclair, D. — 2008-11-12

The most common approach to automatic summarization and highlight detection in sports video is to train an automatic classifier to detect semantic highlights based on occurrences of low-level features such as action replays, excited commentators or changes in a scoreboard. We propose an alternative approach based on the detection of perception concepts (PCs) and the construction of Petri-Nets, which can be used for both semantic description and event detection within sports videos. Low-level algorithms to detect PCs using visual, aural and motion characteristics are proposed, and a series of Petri-Nets composed of PCs is formally defined to describe video content. We call this a perception concept network–Petri-Net (PCN–PN) model. Using PCN–PNs, personalized high-level semantic descriptions of video highlights can be facilitated and queries on high-level semantics can be achieved. A particular strength of this framework is that we can easily build semantic detectors based on PCN–PNs to search within sports videos and locate interesting events. Experimental results based on recorded sports video data across three types of sports games (soccer, basketball and rugby), and each from multiple broadcasters, are used to illustrate the potential of this framework.

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

Jasinski, R. — 2008-11-07

Data Mining and Predictive Analytics: Intelligence Gathering and Crime Analysis

Refaat, M. — 2008-10-25

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. — 2008-10-21

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.

Three Generalizations to a Generic Integrated Test Generation Method for Finite State Machines

Kapus-Kolar, M. — 2008-10-17

In a previous paper, we proposed a generic test generation method for deterministic implementations of deterministic finite state machines. The method supports a wide class of testing strategies, multi-criteria optimization and integrated handling of all the usual optimization concerns. The present paper generalizes the method to an even wider class of strategies, to non-deterministic machines and to machines handling data.

Increasing Service Availability in a Wireless Home Network Environment

Lin, C.-Y., Wang, S.-C., Kuo, S.-Y., Chen, C.-Y. — 2008-10-14

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. — 2008-10-14

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. — 2008-10-14

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. — 2008-09-09

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.

Women in Science, Engineering and Technology: Three Decades of UK Initiatives

Harrin, E. — 2008-09-01

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

Saxena, N., Roy, A., Shin, J. — 2008-08-22

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. — 2008-08-21

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. — 2008-08-21

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. — 2008-08-06

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. — 2008-07-24

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.

Enumerating Proofs of Positive Formulae

Dowek, G., Jiang, Y. — 2008-05-27

We provide a semi-grammatical description of the set of normal proofs of positive formulae in minimal predicate logic, i.e. a grammar that generates a set of schemes, from each of which we can produce a finite number of normal proofs. This method is complete in the sense that each normal proof-term of the formula is produced by some scheme generated by the grammar. As a corollary, we get a similar description of the set of normal proofs of positive formulae for a large class of theories including simple type theory and System F.

Congruence Formats for Weak Readiness Equivalence and Weak Possible Future Equivalence

Huang, X., Jiao, L., Lu, W. — 2008-04-18

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.

Realizing Comprehensive User Profile as the Core Element of Adaptive and Personalized Communication Environments and Systems

Germanakos, P., Tsianos, N., Lekkas, Z., Mourlas, C., Samaras, G. — 2008-04-04

Challenges today in the Web personalization and adaptation research area range from heterogeneous user needs and user environment issues such as current location and time to multi-channel delivery of applications concerning Web-based content related to services, educational multimedia, entertainment, commerce, etc. Nowadays, most Web personalization systems implement various techniques to extract the user profiles, which serve as the main component of such systems. Based on given user preferences and navigation behavior, the Web-based content returns the requested personalized result. The main scope of this paper is to present the various techniques employed by such systems with regard to extraction of user profiles and to introduce a comprehensive user profilethat includes user perceptual preference characteristics. It further analyzes the main intrinsic user characteristics such as visual, cognitive and emotional-processing parameters that are incorporated as well as the ‘traditional’ user profile characteristics that together tend to give the most optimized, adapted and personalized outcome. It finally presents a Web adaptation and personalization system that implements the proposed comprehensive user profile as well as the initial evaluation results.

Implementation of Learning Path in Process Control Model

Luo, J., Kong, W., Ge, L. — 2008-03-26

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. — 2008-03-15

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.

Searching for Expertise: Experiments with the Voting Model

Macdonald, C., Ounis, I. — 2008-03-06

In an expert search task, the user's need is to identify people who have relevant expertise to a topic of interest. An expert search system predicts and ranks the expertise of a set of candidate persons with respect to the user's query. In this work, we propose a novel approach for estimating and ranking candidate expertise with respect to a query. We see the problem of ranking experts as a voting problem, which we model using adaptations of data fusion techniques. We extensively investigate the effectiveness of the voting approach and the associated data fusion techniques across a range of document weighting models, in the context of the TREC 2005 and TREC 2006 Enterprise track settings. The evaluation results show that the voting paradigm is very effective, without using any collection-specific heuristics. Additionally, we further analyse two main features of the voting model, namely the manner in which document votes are combined and the effect of the underlying document ranking. First, for the combination of document votes, we hypothesise that candidate with large profiles can introduce bias in the generated ranking of candidates. We propose and integrate into the model a candidate length normalisation technique that removes bias towards prolific candidate experts. Secondly, we investigate the relative effects of applying various retrieval enhancing techniques to improve the quality of the underlying document ranking, to investigate how each technique improves the retrieval effectiveness of the generated ranking of candidates. At each stage, we experiment extensively and draw conclusions. Our results show that the voting techniques proposed are indeed effective, across several different document weighting models and settings. Secondly, we see that candidate profile length normalisation can help improve retrieval accuracy when applied to the candidate profile sets. Lastly, we show that increasing the quality of the underlying ranking of candidates can enhance the retrieval accuracy of the generated ranking of candidates.

Smart-Context: A Context Ontology for Pervasive Mobile Computing

Moore, P., Hu, B., Wan, J. — 2008-03-04

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. — 2008-02-11

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. — 2008-01-31

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. — 2008-01-22

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. — 2008-01-19

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. — 2008-01-17

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.

Interest Drifts in User Profiling: A Relevance-Based Approach and Analysis of Scenarios

Godoy, D., Amandi, A. — 2008-01-04

For personal information agents, user profiles have to represent user interests and preferences in order to satisfy long-term information needs. An implicit assumption in user-profiling is the existence of persistent interests which, however, might suffer some changes over time. Each time the interests of a user change, his profile becomes inaccurate and the predictive quality decreases. Adaptation of user profiles is, therefore, an essential requirement for personal agents that need to be capable of adjusting their behavior quickly in order to shorten the period of reduced predictive quality. In this paper, a user-profiling technique named WebProfiler, which learns a hierarchical representation of user interests using conceptual clustering, is augmented with an adaptation strategy based on relevance feedback and time-based forgetting in order to deal with drifting interests. We empirically evaluate the performance of this strategy by analyzing its behavior on multiple scenarios of interest drifts and shifts.

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

Zhang, B., Shi, Y., Xiao, X. — 2007-12-21

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. — 2007-12-14

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. — 2007-12-08

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. — 2007-12-02

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.

Test Sequence Generation For Integration Testing Of Component Software

Gallagher, L., Offutt, J. — 2007-11-22

Ensuring high object interoperability is a goal of integration testing for object-oriented (OO) software. When messages are sent, objects that receive them should respond as intended. Ensuring this is especially difficult when software uses components that are developed by different vendors, in different languages, and the implementation sources are not all available. A finite state machines model of inter-operating OO classes was presented in a previous paper. The previous paper presented details of the method and empirical results from an automatic tool. This paper presents additional details about the tool itself, including how test sequences are generated, how several difficult problems were solved and the introduction of new capabilities to help automate the transformation of test specifications into executable test cases. Although the test method is not 100% automated, it represents a fresh approach to automated testing. It follows accepted theoretical procedures while operating directly on OO software specifications. This yields a data flow graph and executable test cases that adequately cover the graph according to classical graph coverage criteria. The tool supports specification-based testing and helps to bridge the gap between theory and practice.

Detection Of Normal and Novel Behaviours In Ubiquitous Domestic Environments

Rivera-illingworth, F., Callaghan, V., Hagras, H. — 2007-11-09

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. — 2007-10-19

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. — 2007-10-18

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.

Automated Worst-Case Execution Time Analysis Based on Program Modes

Ji, M.-L., Wang, J., Li, S., Qi, Z.-C. — 2007-09-26

A program mode is a regular trajectory of the execution of a program that is determined by the values of its input variables. By exploiting program modes, we may make worst-case execution time (WCET) analysis more precise. This paper presents a novel method to automatically find program modes and calculate the WCET estimates of programs. First, the modes of a program will be identified automatically by mode-relevant program slicing, and the precondition will be calculated for each mode using a path-wise test data generation method. Then, for each feasible mode, we show how to calculate its WCET estimate for modern reduced instruction set computer (RISC) processors with caches and pipelines and for traditional complex instruction set computer (CISC) processors. We also present a method to obtain the symbolic expression for each mode for CISC processors. The experimental results show the effectiveness of the method.

Guest Editorial to the Special Issue on Automation of Software Testing

Zhu, H., Cheung, S. C., Horgan, J. R., Jenny Li, J. — 2007-09-25

JEAN TABAKA, Collaboration Explained: Facilitation Skills for Software Project Leaders. Addison Wesley 2006. ISBN-13 978-0321268778. {pound}31.99. 412 pp. Softbound

Harrin, E. — 2007-09-05

YVES POCHET AND LAURENCE A. WOLSEY, Production Planning Using Mixed Integer Programming. Springer 2006. ISBN 978-0-387-29959-4. {pound}38.50/$59.95. 477 pp. Hardbound

Marecek, J. — 2007-09-05

UML Activity Diagram-Based Automatic Test Case Generation For Java Programs

Chen, M., Qiu, X., Xu, W., Wang, L., Zhao, J., Li, X. — 2007-08-25

Test case generation based on design specifications is an important part of testing processes. In this paper, Unified Modeling Language activity diagrams are used as design specifications. By setting up several test adequacy criteria with respect to activity diagrams, an automatic approach is presented to generate test cases for Java programs. Instead of directly deriving test cases from activity diagrams, this approach selects test cases from a set of randomly generated ones according to a given test adequacy criterion. In the approach, we first instrument a Java program under testing according to its activity diagram model, and randomly generate abundant test cases for the program. Then, by running the instrumented program we obtain the corresponding program execution traces. Finally, by matching these traces with the behavior of the activity diagram, a reduced set of test cases are selected according to the given test adequacy criterion. This approach can also be used to check the consistency between the program execution traces and the behavior of activity diagrams.

Using Coupling-Based Weights for the Class Integration and Test Order Problem

Abdurazik, A., Offutt, J. — 2007-08-07

During component-based and object-oriented software development, software classes exhibit relationships that complicate integration, including method calls, inheritance and aggregation. Classes are integrated and tested in specific orders, where each class is added and tested one by one to see if it integrates successfully. A difficulty arises when cyclic dependencies exist—the functionality that is used by the first class to be tested must be mimicked by creating ‘stubs’ (sometimes called ‘mock objects’), an expensive and error-prone operation. This problem is generally called the class integration and test order (CITO) problem, and solutions must fully be automated for integration and testing to proceed smoothly and efficiently. This paper describes new techniques and algorithms to solve the CITO problem. New results include improved edge weights to more precisely model the cost of stubbing, and the use of node weights, which allows more information to be used. These weights are derived from quantitative measures of couplings between the integrated and the stubbed classes. Also, a new algorithm for computing the integration and test orders is presented. The technique is compared with an existing approach and found to be cheaper, get the same results when using edge weights exclusively, and yield better results when using node weights.

Generating Structurally Complex Test Cases By Data Mutation: A Case Study Of Testing An Automated Modelling Tool

Shan, L., Zhu, H. — 2007-06-28

Generation of adequate test cases is difficult and expensive, especially for testing software systems whose input is structurally complex. This paper presents an approach called data mutation to generating a large number of test data from a few seed test cases. It is inspired by mutation testing methods, but differs from them in the aim and the way that mutation operators are defined and used. While mutation testing is a method for measuring test adequacy, data mutation is a method of test case generation. In traditional mutation testing, mutation operators are used to transform the program under test. In contrast, mutation operators in our approach are applied on input data to generate test cases, hence called data mutation operators. The paper reports a case study with the method on testing an automated modelling tool to illustrate the applicability of the proposed method. Experiment data clearly demonstrate that the method is adequate and cost effective, and able to detect a large proportion of faults.

A Survey of Coverage-Based Testing Tools

Yang, Q., Li, J. J., Weiss, D. M. — 2007-05-25

Test coverage is sometimes used to measure how thoroughly software is tested and developers and vendors sometimes use it to indicate their confidence in the readiness of their software. This survey studies and compares 17 coverage-based testing tools primarily focusing on, but not restricted to, coverage measurement. We also survey features such as program prioritization for testing, assistance in debugging, automatic generation of test cases and customization of test reports. Such features make tools more useful and practical, especially for large-scale, commercial software applications. Our initial motivations were both to understand the available test coverage tools and to compare them to a tool that we have developed, called eXVantage (a tool suite that includes code coverage testing, debugging, performance profiling and reporting). Our study shows that each tool has some unique features tailored to its application domains. The readers may use this study to help pick the right coverage testing tools for their needs and environment. This paper is also valuable to those who are new to the practice and the art of software coverage testing, as well as those who want to understand the gap between industry and academia.