The Computer Journal - Advance Access

Privacy on the Line: The Politics of Wiretapping and Encryption, Updated and Expanded Edition

Raymond Choo, K.-K. — 2008-05-02

Design and Performance Evaluation of a Transport Protocol for Ad hoc Networks

Anastasi, G., Ancillotti, E., Conti, M., Passarella, A. — 2008-05-02

Providing efficient transport services over multi-hop ad hoc networks is a fundamental building block for this wireless technology. The typical approach is modifying transmission control protocol (TCP) to fix one (or a few of) its inefficiency while preserving compatibility with the original protocol. However, a complete solution should include a significant number of modifications, such that the original TCP design is deeply modified. In this paper we explore a different approach. We include the desired modifications to TCP in the design of a new transport protocol [transport protocol for ad-hoc (TPA)]. In this way we are able to blend together these features in a unique design framework, and better control interactions among the different (modified) components. We then compare TCP and TPA through field tests, in terms of throughput and total number of transmitted segments. We consider several possible configurations of the protocol parameters, different routing protocols and various networking scenarios. In all the cases taken into consideration, TPA significantly outperforms TCP. To achieve a more thorough understanding of the TPA behaviour, we compare TPA and TCP also in terms of fairness and scalability (both in static and mobile configurations) over a wide range of representative topologies. To this end, we adopt a simulation approach, which is more suitable to this kind of analysis. Simulation results confirm field tests, and show that TPA is able to outperform TCP with respect to all analysed performance figures.

The Future of Computer Technology and its Implications for the Computer Industry

Furber, S. — 2008-04-27

Progress in computer technology over the last four decades has been spectacular, driven by Moore's law which, though initially an observation, has become a self-fulfilling prophecy and a boardroom planning tool. Although Gordon Moore expressed his vision of progress simply in terms of the number of transistors that could be manufactured economically on an integrated circuit, the means of achieving this progress was based principally on shrinking transistor dimensions, and with that came collateral gains in performance, power-efficiency and, last but not least, cost. The semiconductor industry appears to be confident in its ability to continue to shrink transistors, at least for another decade or so, but the game is already changing. We can no longer assume that smaller circuits will go faster, or be more power-efficient. As we approach atomic limits, device variability is beginning to hurt, and design costs are going through the roof. These are impacting the economics of design in ways that will affect the entire computing and communications industries. For example, on the desktop there is a trend away from high-speed uniprocessors towards multi-core processors, despite the fact that general-purpose parallel programming remains one of the greatest unsolved problems of computer science. If computers are to benefit from future advances in technology then there are major challenges ahead, involving understanding how to build reliable systems on increasingly unreliable technology and how to exploit parallelism increasingly effective, not only to improve performance, but also to mask the consequences of component failure. Biological systems demonstrate many of the properties we aspire to incorporate into our engineered technology, so perhaps that suggests a possible source of ideas that we could seek to incorporate into future novel computation systems?

Obituary: Appreciation of Professor Colin Tully (1936-2007): Professor of Software Practice, Middlesex University

2008-04-18

Colin was Emeritus Professor of Software Practice at Middlesex University from where he retired only recently. He started his career at LEO Computers in the 1950s later joined me at the London School of Economics as a Research Fellow before moving on to York University, then returned to industry before being recruited by Middlesex University to inter alia oversee their research activities in computer science. He was a significant contributor to our understanding of the role of software in the overall system. Since his retirement he has been one of the most active members of the group of 23 academics who have expressed concern about the NHS NPfIT. He will be greatly missed both as a colleague and friend.

Comments on the BCS Lecture 'The Future of Computer Technology and its Implications for the Computer Industry' by Professor Steve Furber

2008-04-18

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.

Serum Proteomic Abnormality Predating Screen Detection of Ovarian Cancer

2008-04-15

Ovarian cancer is characterized by vague, non-specific symptoms, advanced stage at diagnosis and poor overall survival. A nested case control study was undertaken on stored serial serum samples from women who developed ovarian cancer and healthy controls (matched for serum processing and storage conditions as well as attributes such as age) in a pilot randomized controlled trial of ovarian cancer screening. The unique feature of this study is that the women were screened for up to 7 years. The serum samples underwent prefractionation using a reversed-phase batch extraction protocol prior to MALDI-TOF MS data acquisition. Our exploratory analysis shows that combining a single MS peak with CA125 allows statistically significant discrimination at the 5% level between cases and controls up to 12 months in advance of the original diagnosis of ovarian cancer. Such combinations work much better than a single peak or CA125 alone. This paper demonstrates that mass spectra from the low molecular weight serum proteome carry information useful for early detection of ovarian cancer. The next step is to identify the specific biomarkers that make early detection possible.

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.

On Formalizing and Normalizing Role-Based Access Control Systems

Power, D., Slaymaker, M., Simpson, A. — 2008-04-03

Role-based access control (RBAC) has emerged as the dominant access control paradigm for service-oriented systems, with this dominance being reflected by the popularity of RBAC both with the research community and with information technology vendors. RBAC's dominance was solidified in 2004 when an American National Standards Institute standard for RBAC was approved. In this paper, we consider some of the drawbacks of this standard and show how the formal description technique, Z, has been used to underpin a model of RBAC. The model builds on the work of Li et al. and adopts a modular approach. In particular, we consider the relationships between different types of inheritance within our model. We show our model can be used to define a notion of equivalence between different RBAC systems. Finally, we show how—via our model—a particular RBAC system can be normalized to produce a simpler—but semantically equivalent—representation. We illustrate this process via two examples.

Aggregation Dynamics in Overlay Networks and Their Implications for Self-Organized Distributed Applications

Saffre, F., Tateson, R., Halloy, J., Shackleton, M., Deneubourg, J. L. — 2008-03-31

In this paper, we investigate the global self-aggregation dynamics arising from local decision-based rewiring of an overlay network, used as an abstraction for an autonomic service-oriented architecture. We measure the ability of a selected set of local rules to foster self-organization of what is originally a random graph into a structured network. Scalability issues with respect to the key parameters of system size and diversity are extensively discussed. Conflicting goals are introduced, in the form of a population of nodes actively seeking to acquire neighbours of a type different from their own, resulting in decreased local homogeneity. We show that a ‘secondary’ self-organization process ensues, whereby nodes spontaneously cluster according to their implicit objective. Finally, we introduce dynamic goals by making the preferred neighbour type a function of the local characteristics of a simulated workload. We demonstrate that in this context, an overlay rewiring process based purely on local decisions and interactions can result in efficient load-balancing without central planning. We conclude by discussing the implications of our findings for the design of future distributed applications, the likely influence of other factors and of extreme parameter values on the ability of the system to self-organize and the potential improvements to our framework.

Synchronized Interactions in Spiked Neuronal Networks

Gelenbe, E., Timotheou, S. — 2008-03-31

The study of artificial neural networks has originally been inspired by neurophysiology and cognitive science. It has resulted in a rich and diverse methodology and in numerous applications to machine intelligence, computer vision, pattern recognition and other applications. The random neural network (RNN) is a probabilistic model which was inspired by the spiking behaviour of neurons, and which has an elegant mathematical treatment that provides both its steady-state behaviour and offers efficient learning algorithms for recurrent networks. Second-order interactions, where more than one neuron jointly act upon other cells, have been observed in nature; they generalize the binary (excitatory–inhibitory) interaction between pairs of cells and give rise to synchronous firing (SF) by many cells. In this paper, we develop an extension of the RNN to the case of synchronous interactions, which are based on two cells that jointly excite a third cell; this local behaviour is in fact sufficient to create SF by large ensembles of cells. We describe the system state and derive its stationary solution as well as a O(N³) gradient descent learning algorithm for a recurrent network with N cells when both standard excitatory–inhibitory interactions, as well as SF, are present.

An Appreciation of Dina St Johnston (1930-2007) Founder of the UK's First Software House

Lavington, S. — 2008-03-26

In the 1950s there was no software industry. Dina St Johnston, who had learned to program whilst working for the computer manufacturer Elliott-Automation, founded Vaughan Programming Services in 1959. The company began to specialise in on-line systems for digital process control at a time when industrial automation was in its infancy. In due course the company developed its own platform-independent, timesharing, mini-operating system (MACE) and, in 1970, the Vaughan 4M microprocessor. Vaughan went on to become specialists in the supply of real time controllers for passenger railways. Dina St Johnston remained an active programmer until 1996.

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 Predictive Video-on-Demand Bandwidth Management Using the Kalman Filter over Heterogeneous Networks

Huang, C.-M., Lin, C.-W., Lin, X.-Y. — 2008-03-18

In order to adapt the quality of an on-demand video stream over a time-varying bandwidth channel, a network-aware bandwidth estimation and rate control scheme are required. This paper proposes a predictive video-on-demand (VoD) bandwidth management and a feedback-based buffer control scheme for streaming fine granular scalability videos over wired/WLAN/3G networks. The predictive VoD bandwidth management includes two parts: bandwidth estimation and rate adaptation. According to the measured information of packet round-trip-time, loss-rate, delay jitter and received bit-rate, an improved Kalman filter is proposed to predict an available bandwidth recursively, and to determine a proper transmission rate in consideration of buffer fullness of a decoder. The optimal parameters of the Kalman filter, e.g. a transition matrix and error covariances, can be initialized, converged and adapted to characteristics of the current network. In our experiments, distinct network traffic models are simulated in comparison with pathChirp and one Republic of China patent. The corresponding estimation results with respect to network information are also exhibited in the real networks.

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.

Editorial

Murtagh, F. — 2008-03-11

Super-Resolution: A Short Review, A New Method Based on Hidden Markov Modeling of HR Image and Future Challenges

Mohammad-Djafari, A. — 2008-03-07

Super-resolution (SR) is the area of research and development which produces one or a set of high-resolution images from one or a set of low-resolution frames. In this paper, first, a short review of a variety of SR problems is presented. Then, starting by a single input single output case, we present different forward modeling of 1D or 2D SR problems. We focus then on the multi input single output and multi input multi output SR problems and provide a summary of recent contributions to them. Then, the SR problem is considered as an inverse problem. A general forward-modeling and inversion framework is presented, which gives the possibility to understand the basics of several classical SR methods and to discuss some important open problems of SR. Specifically, we discuss a different forward modeling, which leads to different classical methods and present our recent inversion methods based on the Bayesian estimation with different prior modeling. In particular, we give the details of a new method, particularly appropriate for piecewise homogeneous images, which provides not only an SR image, but also simultaneously an optimal segmentation of an HR image. Some comparisons of the relative performances of these methods are also presented. Finally, some future challenges in SR are outlined and discussed.

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.

Discussant Contributions for the Computer Journal Lecture

Gelenbe, E. — 2008-03-05

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.

Data Processing in the Early Cosmic Ray Experiments in Sydney

Brennan, M. H. — 2008-02-28

The cosmic ray air shower experiment set up at the University of Sydney in the late 1950s was one of the first complex experiments in Australia to utilize the power of an electronic computer to process and analyse the experimental data. The paper provides a brief overview of the design and construction of the equipment for the experiment and the use of the computer SILLIAC in the processing and analysis of the data. The central role of Chris Wallace in this latter aspect is given special attention.

Multiplier Evolution: A Family of Multiplier VLSI Implementations

Colon-Bonet, G., Winterrowd, P. — 2008-02-27

This paper provides an overview of four floating point multiplier implementations spanning microprocessor designs from 1992 to the present. The algorithm of each multiplier is explored in detail, and key measures of area, delay and design complexity are compared. The approaches span from a simple linear array to a full tree-based network, each targeted at efficient very-large-scale integration implementation. The designs show a progression of implementation techniques encompassing a 20x increase in multiplier performance during this time period.

Vertex-ordering Algorithms for Automatic Differentiation of Computer Codes

Tadjouddine, E.M. — 2008-02-27

In the context of Automatic Differentiation (AD) of functions represented by computer code via the vertex elimination approach first advocated by Griewank and Reese (On the Calculation of Jacobian Matrices by the Markowitz Rule. In Griewank, A. and Corliss, G.F. (eds), Automatic Differentiation of Algorithms: Theory, Implementation and Application, pp. 126–135. SIAM, 1991, Philadelphia, PA.), we present two approximate algorithms based on the linearized computational graph of the input code. The first is a statement-reordering algorithm aiming to tune the AD-generated code so as to maximize its performance for modern superscalar processors. The second is aimed at detecting interface contractions introduced by Bischof and Haghighat (Hierarchical Approaches to Automatic Differentiation. In Berz, M., Bischof, C., Corliss, G. and Griewank, A. (eds), Computational Differentiation: Techniques, Applications, and Tools, pp. 83–94. SIAM, 1996, Philadelphia, PA) in order to enable exploitation of the structure of the input code in the differentiation process. Performance data are also presented.

Super-Resolution in Medical Imaging

Greenspan, H. — 2008-02-19

This paper provides an overview on super-resolution (SR) research in medical imaging applications. Many imaging modalities exist. Some provide anatomical information and reveal information about the structure of the human body, and others provide functional information, locations of activity for specific activities and specified tasks. Each imaging system has a characteristic resolution, which is determined based on physical constraints of the system detectors that are in turn tuned to signal-to-noise and timing considerations. A common goal across systems is to increase the resolution, and as much as possible achieve true isotropic 3-D imaging. SR technology can serve to advance this goal. Research on SR in key medical imaging modalities, including MRI, fMRI and PET, has started to emerge in recent years and is reviewed herein. The algorithms used are mostly based on standard SR algorithms. Results demonstrate the potential in introducing SR techniques into practical medical applications.

Metrics to Evaluate the Use of Object Oriented Frameworks

e Silva, R. P., Freiberger, E. C. — 2008-02-18

The adoption of object-oriented (OO) framework approach can increase the reuse in software development. To reach this goal, however, a high quality OO framework design is needed. Moreover, an OO framework must be used in a proper way. General principles are proposed for OO framework design and use, but it is difficult to evaluate OO framework design and OO framework use in an objective way. This work proposes metrics for quantifying features of OO frameworks and software developed using them. They are useful for evaluating OO framework use and learning how to use it, using statistical comparison with present software based on specific OO frameworks. Additionally, the metrics produce a feedback for OO framework developers. A set of tools developed for automatic gathering and for browsing this kind of information is presented, as well as experimental results.

Some Comments on C. S. Wallace's Random Number Generators

Brent, R. P. — 2008-02-15

We outline some of Chris Wallace's contributions to pseudo-random number generation. In particular, we consider his recent idea for generating normally distributed variates without relying on a source of uniform random numbers and compare it with more conventional methods for generating normal random numbers. Implementations of Wallace's idea can be very fast (approximately as fast as good uniform generators). We discuss the statistical quality of the output, and mention how certain pitfalls can be avoided.

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.

Password-Capabilities and the Walnut Kernel

Castro, M. D., Pose, R. D., Kopp, C. — 2008-02-09

The Walnut kernel is a capability-based operating system kernel that was developed in the Department of Computer Science at Monash University during the 1990s. This kernel is heir to many of the ideas that were implemented in the Password- Capability System. Focusing on the programmer's view, this paper describes the password-capability model and the features of the Walnut kernel and the design decisions taken in creating it. An ANSI compliant standard I/O library is used as an example of the expressive power of the system.

Three Kinds of Probabilistic Induction: Universal Distributions and Convergence Theorems

Solomonoff, R. J. — 2008-02-08

We will describe three kinds of probabilistic induction problems, and give general solutions for each, with associated convergence theorems which show that they tend to give good probability estimates. The first kind extrapolates a sequence of strings and/or numbers. The second extrapolates an unordered set of strings and/or numbers. The third extrapolates an unordered set of ordered pairs of elements that may be strings and/or numbers. Given the first element of a new pair, to get a probability distribution on possible second elements of the pair. Each of the three kinds of problems is solved using an associated universal distribution. In each case a corresponding convergence theorem is given, showing that as sample size grows, the expected error in probability estimate decreases rapidly. The solutions given are very general and cover a great variety of induction problems. Time series prediction, grammar discovery (for both formal and natural languages), curve fitting, the identification problem and the categorization problem, are a few of the kinds of problems amenable to the methods described.

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.

Visual Cryptography Schemes with Reversing

Yang, C.-N., Wang, C.-C., Chen, T.-S. — 2008-01-29

The Visual cryptography scheme (VCS) is a perfect secure method that encrypts a secret image by breaking it into shadow images. A distinctive property of VCS is that one can visually, without computation, decode the secret by superimposing shadow images. However, much of the contrast of the reconstructed image is lost. A different kind of VCS has been recently proposed by Viet and Kurosawa, called VCS with reversing, allowing participants to perform a reversing operation (reverse black and white) on shadow images. Two drawbacks of the Viet–Kurosawa VCS are: (1) one can only reconstruct an almost ideal contrast image but not an ideal contrast image and (2) the Viet–Kurosawa VCS is constructed just from a perfect black VCS. This paper shows a real perfect contrast VCS such that the black and white pixels are perfectly reconstructed within finite runs, no matter what VCS (perfect black or non-perfect black) is used.

The Collective Index: A Technique for Efficient Processing of Progressive Queries

Zhu, Q., Medjahed, B., Sharma, A., Huang, H. — 2008-01-29

The emergence of modern data-intensive applications requires sophisticated database techniques for processing advanced types of user queries on massive data. In this paper, we study such a new type of query, called progressive queries. A progressive query is defined as a set of inter-related and incrementally formulated step-queries. A step-query in a progressive query PQ is specified on the fly based on the results of previously-executed step-queries in PQ. Hence, a progressive query cannot be formulated in advance before its execution, which raises challenges for its processing and optimization. We introduce a query model to characterize different types of progressive queries. We then present a new index structure, called the collective index, to efficiently process progressive queries. The collective index technique incrementally evaluates step-queries via dynamically maintained member indexes. Utilizing the special structure of a collective index, the (member) indexes on the input relation(s) of a step-query are efficiently transformed into indexes on the result relation. Algorithms to efficiently process single-input (unary) linear and multiple-input (join) linear progressive queries based on the collective index are presented. Our experiment results show that the proposed collective index technique outperforms the conventional query processing methods in processing progressive queries.

Reliability and Performance Of Mirrored Disk Organizations

Thomasian, A., Xu, J. — 2008-01-28

Disk mirroring or redundant array of independent disk (RAID) level 1 is a popular paradigm to achieve fault-tolerance and a higher disk access bandwidth for read requests. We consider four RAID1 organizations: basic mirroring (BM), group rotate declustering (GRD), interleaved declustering (ID) and chained declustering (CD). The last three organizations provide a more balanced disk load than BM when a single disk fails, but are more susceptible to data loss than BM when additional disks fail. We compare the four organizations from the viewpoint of: (i) reliability [we quote results from [Thomasian, A. and Blaum, M. (2006) Reliability analysis of mirrored disks. IEEE Trans. Comput., 55, 1640–1644.]] (ii) performability, (iii) performance. In (ii) and (iii), we postulate discrete requests to small randomly placed blocks. For (ii), we compute the mean number of disk requests processed to the point where data loss occurs. For the sake of tractability in (iii), the response time is obtained assuming Poisson arrivals and a first come first serve policy. The ranking from the viewpoint of reliability and performability is: BM, CD, GRD, ID (with two clusters). BM and CD provide the worst performance, ID has a better performance than BM and CD, but is outperformed by GRD. These results are also shown using an asymptotic expansion method. Areas of further research are also discussed, which include the applicability of the mirroring techniques to storage bricks.

Wallace's Approach to Unsupervised Learning: The Snob Program

Jorgensen, M. A., McLachlan, G. J. — 2008-01-27

We describe the Snob program for unsupervised learning as it has evolved from its beginning in the 1960s until its present form. Snob uses the minimum message length principle expounded in Wallace and Freeman (Wallace, C.S. and Freeman, P.R. (1987) Estimation and inference by Compact coding. J. Roy. Statist. Soc. Ser. B, 49, 240–252.) and we indicate how Snob estimates class parameters using the approach of that paper. We will survey the evolution of Snob from these beginnings to the state that it has reached as described by Wallace and Dowe (Wallace, C.S. and Dowe, D.L. (2000) MMM mixture modelling of multi-state, Poisson, Von Mises Circular and Gaussian distributions. Stat. Comput., 10, 73–83.) We pay particular attention to the revision of Snob in the 1980s where definite assignment of things to classes was abandoned.

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.

An Introduction to Reversible Latches

Rice, J. E. — 2008-01-17

Reversible logic has been suggested as one solution to the problem of power consumption in today's electronic devices. This paper addresses the issue of designing reversible latches and provides an overview and analysis of some proposed designs.

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.

A Review of SIMD Multimedia Extensions and their Usage in Scientific and Engineering Applications

Hassaballah, M., Omran, S., Mahdy, Y. B. — 2008-01-17

The volume and complexity of data processed by today's personal computers are increasing exponentially, placing incredible demands on the microprocessors. In the meantime, computing performance that can be achieved by increasing the clock speed of a microprocessor is reaching to physical limits thus making the architectural solutions more prominent. Due to this an important architectural feature is added to recent microprocessors, single instruction multiple data (SIMD), which is a set of instructions that can speed up an application performance by allowing basic operation to be performed on multiple data elements in parallel with fewer instructions. The SIMD computational technique was introduced in the IA-32 Intel^® architecture with MMX technology and then further enhanced with Intel's introduction of streaming SIMD extensions (SSE), SSE 2 (SSE2) and SSE 3 (SSE3). Although programming using these SIMD extensions enables software to achieve higher performance, several exiting scientific applications are not affected. This paper gives an overview of SIMD multimedia extensions. The features of these extensions are introduced. Available methods for programming with multimedia instruction sets are discussed. It also reviews recent trends to use multimedia extensions to accelerate many applications such as multimedia, scientific and engineering applications, and argues for further use in other significant computationally intensive applications.

Selectively Convertible Authenticated Encryption in the Random Oracle Model

Chien, H.-Y. — 2008-01-17

Conventionally, a verified digital signature releases information about both the signing event and the signed content simultaneously, where the signing event proves the truth that someone actually signed something. However, in many cases, the information of the signing event and the signed content have different uses and distinct degrees of importance on various occasions. In such cases, the conventional digital signature, the current authenticated encryption schemes and the current signcryption schemes cannot satisfy the needs of selectively releasing either the information about the signing event or that about the signed content or both depending on the situation. In this paper, we shall propose a selectively convertible authenticated encryption scheme where either the sender or the designated receiver can selectively convert the encryption such that the signing event and that of the signed content can be released adaptively. The security of the scheme is proved in the random oracle model. Applications based on the proposed scheme are also introduced.

Affordance and Symmetry in User Interfaces

Cairns, P., Thimbleby, H. — 2008-01-10

Affordance is a widely used term in human–computer interaction (HCI) that, while familiar and attractive, does not have a clear operational definition. Using the mathematical concept of symmetry, this paper shows that it is possible to begin developing an operational definition for significant aspects of affordance by forming the theoretical concept of symmetry-affordance. The proposed definition restricts symmetry-affordance to particular contexts but in doing so makes it more useful, as it is clear how to exploit symmetry to aid design. The definition is in standard mathematics (in fact, group theory and model theory) and requires little additional structure. In examining symmetry-affordance, it becomes clear that some other HCI notions can be similarly interpreted by symmetry. The paper provides examples and design insights.

Symmetry, as wide or as narrow as you may define its meaning, is one idea by which man through the ages has tried to comprehend and create order, beauty, and perfection. Hermann Weyl [(1952) Symmetry, Princeton University Press, Princeton, NJ]

Universal Usability: Designing Computer Interfaces for Diverse Users

Harrin, E. — 2008-01-08

Computing with Time: From Neural Networks to Sensor Networks

Szymanski, B. K., Chen, G. G. — 2008-01-08

This article advocates a new computing paradigm, called computing with time, that is capable of efficiently performing a certain class of computation, namely, searching in parallel for the closest value to the given parameter. It shares some features with the idea of computing with action potentials proposed by Hopfield, which originated in the field of artificial neuron networks. The basic idea of computing with time is captured in a novel distributed algorithm based on broadcast communication called the lecture hall algorithm, which can compute the minimum among n positive numbers, each residing on a separate processor, using only O(1) broadcasts. When applied to sensor networks, the lecture hall algorithm leads to an interesting routing protocol having several desirable properties.

Analysis of Linear Time Sorting Algorithms

Shutler, P. M. E., Sim, S. W., Lim, W. Y. S. — 2008-01-08

We derive CPU time formulae for the two simplest linear time-sorting algorithms, linear probing sort and bucket sort, as a function of the load factor, and show agreement with experimentally measured CPU times. This allows us to compute optimal load factors for each algorithm, whose values have previously been identified only approximately in the literature. We also present a simple model of cache latency and apply it not only to linear probing sort and bucket sort, where the bulk of the latency is due to random access, but also to the log–linear algorithm quicksort, where the access is primarily sequential, and again show agreement with experimental CPU times. With minor modifications, our model also fits CPU times previously reported by LaMarca and Ladner for radix sort, and by Rahman and Raman for most significant digit radix sort, Flashsort1, and memory tuned quicksort.

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.

The Availability of Complemental k-Coteries

Kuo, Y.-C., Wu, P.-Y. — 2007-12-21

k-Coterie is a graceful concept to solve the distributed k-mutual exclusion problem. The k-mutual exclusion algorithm adopting k-coteries could provide the fault-tolerant capability. The complementalness and the availability are two important metrics to measure the fault-tolerant capability of a k-coterie. Since those two metrics are defined under two different failure assumptions, for a given k-coterie, two independent works to measure those two metrics are necessary. In this paper, we derive the characteristics of the complemental k-coterie on its availability. With the characteristic, verifying the complementalness of a k-coterie and evaluating its availability could be combined together to reduce the redundant works on measuring the fault-tolerant capability of the k-coterie.

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.

The Effect of the Distributed Test Architecture on the Power of Testing

Hierons, R. M., Ural, H. — 2007-12-20

There has been much interest in testing from finite-state machines (FSMs). If the system under test can be modelled by the (minimal) FSM N then testing from an (minimal) FSM M is testing to check that N is isomorphic to M. In the distributed test architecture, there are multiple interfaces/ports and there is a tester at each port. This can introduce controllability/synchronization and observability problems. This paper shows that the restriction to test sequences that do not cause controllability problems and the inability to observe the global behaviour in the distributed test architecture, and thus relying only on the local behaviour at remote testers, introduces fundamental limitations into testing. There exist minimal FSMs that are not equivalent, and so are not isomorphic, and yet cannot be distinguished by testing in this architecture without introducing controllability problems. Similarly, an FSM may have non-equivalent states that cannot be distinguished in the distributed test architecture without causing controllability problems: these are said to be locally s-equivalent and otherwise they are locally s-distinguishable. This paper introduces the notion of two states or FSMs being locally s-equivalent and formalizes the power of testing in the distributed test architecture in terms of local s-equivalence. It introduces a polynomial time algorithm that, given an FSM M, determines which states of M are locally s-equivalent and produces minimal length input sequences that locally s-distinguish states that are not locally s-equivalent. An FSM is locally s-minimal if it has no pair of locally s-equivalent states. This paper gives an algorithm that takes an FSM M and returns a locally s-minimal FSM M' that is locally s-equivalent to M.

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.

Super-Resolution and Blind Deconvolution For Rational Factors With an Application to Color Images

Sroubek, F., Flusser, J., Cristobal, G. — 2007-12-10

In many real applications, traditional super-resolution (SR) methods fail to provide high-resolution images due to objectionable blur and inaccurate registration of input low-resolution images. Only integer resolution enhancement factors, such as 2 or 3, are often considered, but non-integer factors between 1 and 2 are also important in real cases. We introduce a method to SR and deconvolution, which assumes no prior information about the shape of degradation blurs, incorporates registration parameters, and is properly defined for any rational (fractional) resolution factor. The method minimizes a regularized energy function with respect to the high-resolution image and blurs, where regularization is carried out in both the image and blur domains. The blur regularization is based on a generalized multi-channel blind deconvolution constraint derived in the paper. An extension to color images is briefly discussed. Experiments on real data illustrate robustness to noise and other advantages of the method.

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.

Evolutionary Computation for Modeling and Optimization

Baykasoglu, Prof. Dr. A. — 2007-12-02

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.

Efficient Algorithms for Integer Division by Constants Using Multiplication

Cavagnino, D., Werbrouck, A. E. — 2007-11-23

We present a complete analysis of the integer division of a single unsigned dividend word by a single unsigned divisor word based on double-word multiplication of the dividend by an inverse of the divisor. The well-known advantage of this method yields run-time efficiency, if the inverse of the divisor can be calculated at compile time, since multiplication is much faster than division in arithmetic units. Our analysis leads to the discovery of a limit to the straightforward application of this method in the form of a critical dividend, which fortunately associates with a minority of the possible divisors (20%) and defines only a small upper part of the available dividend space. We present two algorithms for ascertaining whether a critical dividend exists and, if so, its value along with a circumvention of this limit. For completeness, we include an algorithm for integer division of a unsigned double-word dividend by an unsigned single-word divisor in which the quotient is not limited to a single word and the remainder is an intrinsic part of the result.

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.

Composition of Self-Adapting Components for Customizable Systems

Pastrana, J.L., Pimentel, E., Katrib, M. — 2007-11-14

Software systems grow each day in size and complexity. In an effort to manage increasing complexity and to maximize the reuse of code, the software engineering community has, in recent years, put considerable effort into the design and development of component-based software methodologies and tools. Inspired by the notion of connector (Allen and Garlan (1994) Formal connectors. Technical report CMU-CS-94-115, Carnegie Mellon University, PA, USA) in software architecture and the ‘Design by Contract’ metaphor proposed by Meyer ((2000) Object-Oriented Software Construction. Prentice Hall, USA), this paper presents a methodology for component composition, coordination and dynamic adaptation. Our proposal is based on connectors enriched with contracts, making software architecture more explicit at the implementation level. Those connectors will be components in our system. Therefore, we can use subtyping techniques for connectors development and we could offer a set of generic connectors implementing standard behavior patterns. In addition, the connectors will use semantic web techniques and a Prolog machine to solve functional adaptation problems, such us name or parameters mismatching of a service, at run-time.

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.

Bayesian Methods for Image Super-Resolution

Pickup, L. C., Capel, D. P., Roberts, S. J., Zisserman, A. — 2007-10-27

We present a novel method of Bayesian image super-resolution in which marginalization is carried out over latent parameters such as geometric and photometric registration and the image point-spread function. Related Bayesian super-resolution approaches marginalize over the high-resolution image, necessitating the use of an unfavourable image prior, whereas our method allows for more realistic image prior distributions, and reduces the dimension of the integral considerably, removing the main computational bottleneck of algorithms such as Tipping and Bishop's Bayesian image super-resolution. We show results on real and synthetic datasets to illustrate the efficacy of our method.

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.

Restoration of Bayer-sampled Image Sequences

Gevrekci, M., Gunturk, B. K., Altunbasak, Y. — 2007-10-17

Spatial resolution of digital images are limited due to optical/sensor blurring and sensor site density. In single-chip digital cameras, the resolution is further degraded because such devices use a color filter array to capture only one spectral component at a pixel location. The process of estimating the missing two color values at each pixel location is known as demosaicking. Demosaicking methods usually exploit the correlation among color channels. When there are multiple images, it is possible not only to have better estimates of the missing color values but also to improve the spatial resolution further (using super-resolution reconstruction). In this paper, we propose a multi-frame spatial resolution enhancement algorithm based on the projections onto convex sets technique.

Heuristic-Guided Abstraction Refinement

He, F., Song, X., Gu, M., Sun, J. — 2007-10-11

Model checking has been considered as a promising approach to establish the correctness of systems. Counterexample-guided abstraction refinement is a key strategy for model checking in verification of large-scale systems. State separation problem poses the main hurdle during the refinement. We present two fast heuristics to solve this problem. We prove the effectiveness of our heuristics by both theoretical analysis and experimental results. Experimental results show the promising performance of our approach.

High Dynamic Range Image Reconstruction with Spatial Resolution Enhancement

Choi, J., Park, M. K., Kang, M. G. — 2007-10-04

For the last two decades, two related approaches have been studied independently in conjunction with limitations of image sensors. The one is to reconstruct a high-resolution (HR) image from multiple low-resolution (LR) observations suffering from various degradations such as blur, geometric deformation, aliasing, noise, spatial sampling and so on. The other one is to reconstruct a high dynamic range (HDR) image from differently exposed multiple low dynamic range (LDR) images. LDR is due to the limitation of the capacitance of analogue-to-digital converter and the nonlinearity of the imaging system's response function. In practical situations, since observations suffer from limitations of both spatial resolution and dynamic range, it is reasonable to address them in a unified context. Most super-resolution (SR) image reconstruction methods that enhance the spatial resolution assume that the dynamic ranges of observations are the same or the imaging system's response function is already known. In this paper, the conventional approaches are overviewed and the SR image reconstruction, which simultaneously enhances spatial resolution and dynamic range, is proposed. The image degradation process including limited spatial resolution and limited dynamic range is modelled. With the observation model, the maximum a posteriori estimates of the response function of the imaging system as well as the single HR image and HDR image are obtained. Experimental results indicate that the proposed algorithm outperforms the conventional approaches that perform the HR and HDR reconstructions sequentially with respect to both objective and subjective criteria.

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

Modeling ODP Computational Specifications Using UML

Romero, J. R., Troya, J. M., Vallecillo, A. — 2007-09-12

The open distributed processing (ODP) computational viewpoint describes the functionality of a system and its environment in terms of a configuration of objects interacting at interfaces, independently of their distribution. Quality of service (QoS) contracts and service level agreements are an integral part of any computational specification, which are specified in ODP in terms of environment contracts. Up until unified modeling language (UML) version 2, both the lack of precision in the UML definition and the semantic gap between the ODP concepts and the UML constructs hindered its application for ODP computational viewpoint modeling. With the advent of UML 2 the situation has changed, because its semantics have been more precisely defined and it now incorporates a whole new set of concepts more apt for modeling the structure and behavior of distributed systems. In this paper, we explore the benefits provided by the new extension mechanisms of UML for modeling the ODP computational specifications and, in particular, we show how ODP environment contracts can be modeled with this approach.

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

Evaluation of Economy in a Zero-sum Perfect Information Game

Iqbal, A. — 2007-09-05

A zero-sum perfect information game is one where every player knows all the moves. Chess is a good example where the object is to checkmate or capture the enemy king. One important feature of checkmates, especially in chess problem composition, is economy. This paper proposes a computational function to evaluate the economy of checkmate configurations on the chessboard. Several experiments were performed comparing chess compositions and regular games to validate the function. The results suggest that the proposed evaluation function is able to correctly discern economical differences in checkmate positions to a high degree of statistical significance and correlates positively with the perception of human chess players. This evaluation function can therefore be useful in increasing the versatility of chess database search engines, as a component in aesthetic models of chess and aiding judges in chess composition tournaments.

Application Of Papoulis Gerchberg Method In Image Super-Resolution and Inpainting

Chatterjee, P., Mukherjee, S., Chaudhuri, S., Seetharaman, G. — 2007-09-04

In this paper, we study the Papoulis–Gerchberg (PG) method and its applications to domains of image restoration such as super-resolution (SR) and inpainting. We show that the method performs well under certain conditions. We then suggest improvements to the method to achieve better SR and inpainting results. The modification applied to the SR process also allows us to apply the method to a larger class of images by doing away with some of the restrictions inherent in the classical PG method. We also present results to demonstrate the performance of the proposed techniques.

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.

Inpainting and Zooming Using Sparse Representations

Fadili, M.J., Starck, J.-L., Murtagh, F. — 2007-07-29

Representing the image to be inpainted in an appropriate sparse representation dictionary, and combining elements from Bayesian statistics and modern harmonic analysis, we introduce an expectation maximization (EM) algorithm for image inpainting and interpolation. From a statistical point of view, the inpainting/interpolation can be viewed as an estimation problem with missing data. Toward this goal, we propose the idea of using the EM mechanism in a Bayesian framework, where a sparsity promoting prior penalty is imposed on the reconstructed coefficients. The EM framework gives a principled way to establish formally the idea that missing samples can be recovered/interpolated based on sparse representations. We first introduce an easy and efficient sparse-representation-based iterative algorithm for image inpainting. Additionally, we derive its theoretical convergence properties. Compared to its competitors, this algorithm allows a high degree of flexibility to recover different structural components in the image (piecewise smooth, curvilinear, texture, etc.). We also suggest some guidelines to automatically tune the regularization parameter.

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.