bluuebunny/crossref_metadata_2025 huggingface dataset:
WAVE FUNCTION AND PAIR DISTRIBUTION FUNCTION OF A DILUTE BOSE GAS
Authors: WEI BO-BO
Published: June 2009

The wave function of a dilute hard sphere Bose gas at low temperatures is revisited. Errors in an early 1957 paper are corrected. The pair distribution function is calculated for two values of [Formula: see text].
GLOBAL AND EXPONENTIAL ATTRACTORS FOR THE PENROSE–FIFE SYSTEM
Authors: SCHIMPERNA GIULIO
Published: June 2009

The Penrose–Fife system for phase transitions is addressed. Dirichlet boundary conditions for the temperature are assumed. Existence of global and exponential attractors is proved. Differently from preceding contributions, here the energy balance equation is both singular at 0 and degenerate at ∞. For this reason, the dissipativity of the associated dynamical process is not trivial and has to be proved rather carefully.
PREDICTION OF EMISSIONS USING COMBUSTION PARAMETERS IN A DIESEL ENGINE THROUGH FUZZY LOGIC TECHNIQUES
Authors: BOSE N. , KUMAR N. SENTHIL
Published: June 2009

The present generation faces a major problem due to pollution. The pollution from diesel engines contributes to nearly 33% of the total atmospheric on-road vehicle pollution. Diesel engine contributes more smoke and oxides of nitrogen (NOx) which are harmful to the health and environment. Preventive steps could be taken if these emissions are predicted. In this paper, the prediction of smoke and NOx has been attempted through fuzzy logic techniques. Using fuzzy logic, intermediate values could be defined between conventional evaluations. The combustion parameters considered for prediction of emissions are load, peak pressure, indicated mean effective pressure, combustion duration, and ignition delay. Based on the engine system, rules have been framed. The pollutants NOx and smoke are the output parameters. On comparison, the actual experimental readings and the values through fuzzy logic show a good correlation. Since there is a good correlation, NOx and smoke can be predicted for any intermediate load conditions. This helps the manufacturers to meet the emission regulations for Euro norms.
GA-BASED OPTIMIZATION OF TAPERING WINDOWS FOR ARTIFACT REDUCTION IN FOURIER ELECTRON MAGNETIC RESONANCE IMAGES
Authors: SUMATHI M. , KRISHNA MURALI C. , MURUGESAN R.
Published: June 2009

Optimization of tapering windows for artifact reduction in two-dimensional (2D) Fourier electron magnetic resonance (EMR) tomography using genetic algorithm (GA) is presented. EMR imaging (EMRI) is a fast emerging functional imaging modality for studying free radicals in biological systems. EMRI by single point imaging (SPI) modality is a Fourier imaging technique. The bioclearance of the imaging agent as well as the need to minimize the radio frequency power deposition on the live animals, dictate reduced k-space sampling. This leads to ringing (Gibbs) artifacts in both directions of the 2D image, because, unlike the conventional MRI, SPI is phase encoding in both directions. To dampen the high-frequency components, data tapering windows are multiplicatively applied to provide tolerable blurred resultant image with reduced Gibbs ringing. To find a compromise between blur and ringing artifact, in this paper a method of optimizing the window functions by using GA is proposed. Our experiments suggest GA-based Kaiser window shows better performance by visual as well as quantitative evaluation.
ON THE USE OF INTELLIGENT AGENTS TO GUIDE TEST SEQUENCE SELECTION AND OPTIMIZATION
Authors: MALA D. JEYA , MOHAN V.
Published: June 2009

Many of the automated testing tools concentrate on the automatic generation of test cases but do not worry about their optimization. In our paper, we analyzed the system model, which is represented as a state diagram and selected a very limited set of test sequences to be executed from the extreme large number (usually infinitely many) of potential ones. This paper demonstrates a way to generate optimal test sequences that are guaranteed to take the least possible time to execute and also satisfies both state and branch coverage criteria using Intelligent Agents.

In the proposed approach, the Intelligent Search Agent (ISA) takes the decision of optimized test sequences by searching through the SUT, which is represented as a graph in which each node is associated with a heuristic value and each edge is associated with an edge weight. The Intelligent Agent finds the best sequence by following the nodes that satisfy the fitness criteria and generates the optimized test sequences for the SUT. Finally we compared our approach with existing Ant Colony Optimization (ACO)-based test sequence optimization approach and proved that our approach produces better results.
STABILIZING NETWORKED PNEUMATIC CONTROL SYSTEMS WITH TIME DELAYS
Authors: HONG MING-WEI , LIN CHUN-LIANG , SHIU BING-MIN , AOUF NABIL
Published: June 2009

It has been known that time delays may not only degrade the performance of the closed-loop control systems, but also induce instability due to the introduction of extra phase lag. The focus of this paper is to find out a way to design a robust controller for networked control systems (NCSs) with time-varying communication delays. To this aim, a mixed fuzzy-PID/neural network compensating scheme is proposed so as to alleviate the influence resulting from uncertain communication delays while maintaining system performance. A condition ensuring stability of the NCS is derived from the system's input–output viewpoint. The effectiveness and superiority of our proposed approach are fully verified in an experimentally networked pneumatic control system.
MULTI-OBJECTIVE GA-OPTIMIZED INTERPOLATION KERNELS FOR RECONSTRUCTION OF HIGH RESOLUTION EMR IMAGES FROM LOW-SAMPLED K-SPACE DATA
Authors: BALASUBRAMANIAN D. , KRISHNA MURALI C. , MURUGESAN R.
Published: June 2009

The low-frequency instrumentation and imaging capabilities facilitate electron magnetic resonance imaging (EMRI) as an emerging non-invasive imaging technology for mapping free radicals in biological systems. Unlike MRI, EMRI is implemented as a pure phase–phase encoding technique. The fast bio-clearance of the imaging agent and the requirement to reduce radio frequency power deposition dictate collection of reduced k-space samples, compromising the quality and resolution of the EMR images. The present work evaluates various interpolation kernels to generate larger k-space samples for image reconstruction, from the acquired reduced k-space samples. Using k-space EMR data sets, acquired for phantom as well as live mice, the proposed technique is critically evaluated by computing quality metrics viz. signal-to-noise ratio (SNR), standard deviation error (SDE), root mean square error (RMSE), peak signal-to-noise ratio (PSNR), contrast-to-noise ratio (CNR) and Lui's error function (F(I)). The quantitative evaluation of 24 different interpolation functions (including piecewise polynomial functions and many windowed sinc functions) to upsample the k-space data for the Fourier EMR image reconstruction shows that at the expense of a slight increase in computing time, the reconstructed images from upsampled data, produced using Spline-sinc, Welch-sinc, and Gaussian-sinc kernels, are closer to reference image with minimal distortion. Support of the interpolating kernel is a characteristic parameter deciding the quality of the reconstructed image and the time complexity. In this paper, a method to optimize the kernel support using genetic algorithm (GA) is also explored. Maximization of the fitness function has two conflicting objectives and it is approached as a multi-objective optimization problem.
CONSTRAINED DISJOINT PATHS IN GEOMETRIC NETWORKS
Authors: GEWALI LAXMI P. , MAZZELLA DAN , SELVARAJ HENRY
Published: June 2009

We address the problem of constructing a pair of node-disjoint paths connecting two given nodes in a geometric network. We propose a simple algorithm for constructing such a path that does not use any complicated data structure which can be easily implemented. We also consider two variations of disjoint path pair problems which we call narrow corridor problem and width-bounded corridor problem and present efficient algorithms for solving them.
QRS COMPLEX DETECTION USING OPTIMAL DISCRETE WAVELET
Authors: KUMARI R. SHANTHA SELVA , BHARATHI S. , SADASIVAM V.
Published: June 2009

Wavelet transform has emerged as a powerful tool for time frequency analysis of complex nonstationary signals such as the electrocardiogram (ECG) signal. In this paper, the design of good wavelets for cardiac signal is discussed from the perspective of orthogonal filter banks. Optimum wavelet for ECG signal is designed and evaluated based on perfect reconstruction conditions and QRS complex detection. The performance is evaluated by using the ECG records from the MIT-BIH arrhythmia database. In the first step, the filter coefficients (optimum wavelet) is designed by reparametrization of filter coefficients. In the second step, ECG signal is decomposed to three levels using the optimum wavelet and reconstructed. From the reconstructed signal, the range of error signal is calculated and it is compared with the performance of other suitable wavelets already available in the literature. The optimum wavelet gives the maximum error range as 10-14–10-11 which is better than that of other wavelets existing in the literature. In the third step, the baseline wandering is removed from the ECG signal for better detection of QRS complex. The optimum wavelet detects all R peaks of all records. That is using optimum wavelet 100% sensitivity and positive predictions are achieved. Based on the performance, it is confirmed that optimum wavelet is more suitable for ECG signal.
SOFTWARE RELIABILITY PREDICTION USING INTELLIGENT TECHNIQUES: APPLICATION TO OPERATIONAL RISK PREDICTION IN FIRMS
Authors: Ravi V. , CHAUHAN NIKUNJ J. , KIRAN N. RAJ
Published: June 2009

In this paper, operational risk arising from the technological dimension is effectively modeled by efficiently forecasting software reliability. We propose the use of wavelet neural networks (WNN) to predict software reliability. Two kinds of wavelets were employed in WNN as transfer functions, viz. Morlet wavelet and Gaussian wavelet, thus giving rise to two variants of WNN. The effectiveness of WNN is demonstrated on a data set taken from literature. Its performance is compared with that of multiple linear regression, multivariate adaptive regression splines, back propagation trained neural network, threshold-accepting trained neural network, threshold accepting trained wavelet neural network, pi-sigma network, general regression neural network, dynamic evolving neuro-fuzzy inference system and TreeNet in terms of normalized root mean square error obtained on test data. Based on the experiments performed, it is observed that the WNN-based models outperformed all the other techniques.
A THEORETICAL FRAMEWORK RELATING TO EXPONENTIALLY FREQUENCY-DEPENDENT SELECTION MODEL IN POLLAK'S SENSE
Authors: SANYAL DULAL CHANDRA , SARKAR BIJAN
Published: June 2009

Allowing the exponentially frequency-dependent fitnesses and taking into consideration the viability effect on the fertility model, a deterministic mathematical model of selection in a one-locus two-allele genetic system has been developed in such a way that equilibrium frequencies of the three genotypes are the same as those of optimizing the mean fertility of the population. Under the consideration of both exponentially increasing and decreasing nature environments in the sense of viability and fertility selections to be opposite, degenerate optimization points have been calculated by verifying whether those equilibrium points are Kuhn–Tucker points or not. The Hadeler–Liberman symmetric fertility model has also been accounted for derivation of all sets of frequencies of this type. Assuming the Fundamental Theorem of Natural Selection, a mathematical expression has been derived to show the variation of mean fertility with generation.
NOTES ON MULTIPLE BIFURCATIONS IN A DELAYED PREDATOR–PREY MODEL WITH NONMONOTONIC FUNCTIONAL RESPONSE
Authors: FAN YONG-HONG , WANG LIN-LIN , WANG MING-XIN
Published: June 2009

By using the normal form theory for RFDE developed by Faria and Magalhaes, the multi-bifurcations for a delayed predator–prey model with nonmonotonic functional response [Formula: see text] have been studied, where a, b, μ, c, m, d, and τ are all nonnegative constants. Our results show that there exists a Bogdanov–Takens bifurcation point of codimension three when τ varies and extend some conclusions in two related articles.
CAPITAL THEORETIC ANALYSIS OF A HOLLING–TANNER-TYPE PREY–PREDATOR FISHERY WITH TAXATION AS A CONTROL INSTRUMENT
Authors: DAS TAPASI , MUKHERJEE R. N. , CHAUDHURI K. S.
Published: June 2009

The level of fishing effort expands or contracts in a dynamic reaction model of a fishery accordingly as the net economic revenue (i.e. perceived rent) to the fishermen is positive or negative. A dynamic reaction model reflects this dynamic interaction between the perceived rent and the effort in a fishery. The combined harvesting of a prey–predator fishery is assumed to be regulated by an external authority by imposing a tax per unit biomass of both the species. The fishing effort is taken to be a dynamic variable of time, which is proportional to the instantaneous capital invested in the fishery. The steady states of the system along with their local as well as global stability are considered. The optimal harvesting policy with the tax as a control instrument is discussed. The results are numerically discussed and graphically illustrated. Sensitivity analysis of the parameters is carried out. The paper ends with concluding remarks.
MATHEMATICAL MODELING AND ANALYSIS OF THE SPREAD OF CARRIER DEPENDENT INFECTIOUS DISEASES: EFFECTS OF CUMULATIVE DENSITY OF ENVIRONMENTAL FACTORS
Authors: SINGH SHIKHA , SHUKLA J. B. , CHANDRA PEEYUSH
Published: June 2009

In this paper, a nonlinear mathematical model with immigration for carrier dependent infectious diseases is proposed and analyzed by considering explicitly the cumulative effect of environmental factors, which are conducive to the growth of carrier population. It is assumed that the density of carrier population is governed by a general logistic model. It is assumed further that the growth rate per capita and the modified carrying capacity of carrier population increase as the cumulative density of environmental factors, governed by population density dependent growth equation, increases. It is shown that as the parameters governing environmental factors increase, the number of infectives in the population increases. It is also found that due to immigration, the disease becomes more endemic.
“Web evolution” by Alex Q. Chen, with Jessica Rubart as coordinator
Authors: Chen Alex Q.
Published: June 2009

Alex Q. Chen is a PhD Student in the School of Computer Science at the University of Manchester. His Master's thesis was entitled "Web Evolution" and involved an analysis of the time difference between the introduction of Web standards and recommendations, such as JavaScript and XHTML, and their widespread adoption by Web developers. Alex is currently studying for a PhD where his interests include Web Mining, Web Accessibility and User-Centered Design.
Up and coming SIGWEB supported conferences
Authors: Deshpande Yogesh
Published: June 2009

SIGWEB supports several specialized conferences, short courses, and workshops, as well as the Annual Hypertext Conference. SIGWEB sponsored conferences focus on timely topics in applied and computational hypertext and Web disciplines and provide a place for members and the entire applied Hypermedia and Web community to exchange ideas and to meet with and expand their network of colleagues. In this article, we provide a brief overview of SIGWEB sponsored conferences, in addition to events that are in cooperation with SIGWEB. During the last six months, the number of SIGWEB cooperating conferences has gone up significantly, as the reader will discover here.
Toward native web execution
Authors: Kroeker Kirk L.
Published: June 2009

Several software projects are narrowing the performance gap between browser-based applications and their desktop counterparts. In the process, they're creating new ways to improve the security of Web-based computing.
ACM award winners
Authors: CACM Staff
Published: June 2009

Among this year's distinguished honorees are Barbara Liskov of Massachusetts Institute of Technology and Jon Kleinberg of Cornell University.
Legally speakingThe dead souls of the Google book search settlement
Authors: Samuelson Pamela
Published: June 2009

Why the Google Book Search settlement agreement under consideration could result in an extensive restructuring of the book industry.
ViewpointWhy computer science doesn't matter
Authors: Felleisen Matthias , Krishnamurthi Shriram
Published: June 2009

Aligning computer science with high school mathematics can help turn it into an essential subject for all students.
Point/counterpointCS education in the U.S.
Authors: Dewar Robert , Astrachan Owen
Published: June 2009

Considering the most effective methods for teaching students the fundamental principles of software engineering.
The five-minute rule 20 years later (and how flash memory changes the rules)
Authors: Graefe Goetz
Published: June 2009

Revisiting Gray and Putzolu's famous rule in the age of Flash.
Probabilistic databases
Authors: Dalvi Nilesh , Ré Christopher , Suciu Dan
Published: June 2009

Treasures abound from hidden facts found in imprecise data sets.
Apprenticeship learning for helicopter control
Authors: Coates Adam , Abbeel Pieter , Ng Andrew Y.
Published: June 2009

Autonomous helicopter flight is widely regarded to be a highly challenging control problem. As helicopters are highly unstable and exhibit complicated dynamical behavior, it is particularly difficult to design controllers that achieve high performance over a broad flight regime.

While these aircraft are notoriously difficult to control, there are expert human pilots who are nonetheless capable of demonstrating a wide variety of maneuvers, including aerobatic maneuvers at the edge of the helicopter's performance envelope. In this paper, we present algorithms for modeling and control that leverage these demonstrations to build high-performance control systems for autonomous helicopters. More specifically, we detail our experiences with the Stanford Autonomous Helicopter, which is now capable of extreme aerobatic flight meeting or exceeding the performance of our own expert pilot.
Formal verification of a realistic compiler
Authors: Leroy Xavier
Published: June 2009

This paper reports on the development and formal verification (proof of semantic preservation) of CompCert, a compiler from Clight (a large subset of the C programming language) to PowerPC assembly code, using the Coq proof assistant both for programming the compiler and for proving its correctness. Such a verified compiler is useful in the context of critical software and its formal verification: the verification of the compiler guarantees that the safety properties proved on the source code hold for the executable compiled code as well.
Graph partitioning using single commodity flows
Authors: Khandekar Rohit , Rao Satish , Vazirani Umesh
Published: June 2009

We show that the sparsest cut in graphs with
n
vertices and
m
edges can be approximated within
O
(log
2
n
) factor in Õ(
m
+ n
3/2
) time using polylogarithmic single commodity max-flow computations. Previous algorithms are based on multicommodity flows that take time Õ(
m
+ n
2
). Our algorithm iteratively employs max-flow computations to embed an expander flow, thus providing a certificate of expansion. Our technique can also be extended to yield an
O
(log
2
n
)-(pseudo-) approximation algorithm for the edge-separator problem with a similar running time.
On the bias of traceroute sampling
Authors: Achlioptas Dimitris , Clauset Aaron , Kempe David , Moore Cristopher
Published: June 2009

Understanding the graph structure of the Internet is a crucial step for building accurate network models and designing efficient algorithms for Internet applications. Yet, obtaining this graph structure can be a surprisingly difficult task, as edges cannot be explicitly queried. For instance, empirical studies of the network of Internet Protocol (IP) addresses typically rely on indirect methods liketracerouteto build what are approximately single-source, all-destinations, shortest-path trees. These trees only sample a fraction of the network's edges, and a paper by Lakhina et al. [2003] found empirically that the resulting sample is intrinsically biased. Further, in simulations, they observed that the degree distribution under traceroute sampling exhibits a power law even when the underlying degree distribution is Poisson.

In this article, we study the bias of traceroute sampling mathematically and, for a very general class of underlying degree distributions, explicitly calculate the distribution that will be observed. As example applications of our machinery, we prove that traceroute sampling finds power-law degree distributions in both δ-regular and Poisson-distributed random graphs. Thus, our work puts the observations of Lakhina et al. on a rigorous footing, and extends them to nearly arbitrary degree distributions.
Empirical hardness models
Authors: Leyton-Brown Kevin , Nudelman Eugene , Shoham Yoav
Published: June 2009

Is it possible to predict how long an algorithm will take to solve a previously-unseen instance of an NP-complete problem? If so, what uses can be found for models that make such predictions? This article provides answers to these questions and evaluates the answers experimentally.

We propose the use of supervised machine learning to build models that predict an algorithm's runtime given a problem instance. We discuss the construction of these models and describe techniques for interpreting them to gain understanding of the characteristics that cause instances to be hard or easy. We also present two applications of our models: building algorithm portfolios that outperform their constituent algorithms, and generating test distributions that emphasize hard problems.

We demonstrate the effectiveness of our techniques in a case study of the combinatorial auction winner determination problem. Our experimental results show that we can build very accurate models of an algorithm's running time, interpret our models, build an algorithm portfolio that strongly outperforms the best single algorithm, and tune a standard benchmark suite to generate much harder problem instances.
Anonymization-based attacks in privacy-preserving data publishing
Authors: Wong Raymond Chi-Wing , Fu Ada Wai-Chee , Wang Ke , Pei Jian
Published: June 2009

Data publishing generates much concern over the protection of individual privacy. Recent studies consider cases where the adversary may possess different kinds of knowledge about the data. In this article, we show that knowledge of the mechanism or algorithm of anonymization for data publication can also lead to extra information that assists the adversary and jeopardizes individual privacy. In particular, all known mechanisms try to minimize information loss and such an attempt provides a loophole for attacks. We call such an attack a minimality attack. In this article, we introduce a model called
m
-confidentiality which deals with minimality attacks, and propose a feasible solution. Our experiments show that minimality attacks are practical concerns on real datasets and that our algorithm can prevent such attacks with very little overhead and information loss.
Efficient reasoning about a robust XML key fragment
Authors: Hartmann Sven , Link Sebastian
Published: June 2009

We review key constraints in the context of XML as introduced by Buneman et al. We demonstrate that:

(1) one of the proposed inference rules is not sound in general, and

(2) the inference rules are incomplete for XML key implication, even for nonempty sets of simple key paths.

This shows, in contrast to earlier statements, that the axiomatizability of XML keys is still open, and efficient algorithms for deciding their implication still need to be developed. Solutions to these problems have a wide range of applications including consistency validation, XML schema design, data exchange and integration, consistent query answering, XML query optimization and rewriting, and indexing.

In this article, we investigate the axiomatizability and implication problem for XML keys with nonempty sets of simple key paths. In particular, we propose a set of inference rules that is indeed sound and complete for the implication of such XML keys. We demonstrate that this fragment is robust by showing the duality of XML key implication to the reachability problem of fixed nodes in a suitable digraph. This enables us to develop a quadratic-time algorithm for deciding implication, and shows that reasoning about this XML key fragment is practically efficient. Therefore, XML applications can be unlocked effectively since they benefit not only from those XML keys specified explicitly by the data designer but also from those that are specified implicitly.
Mostly static program partitioning of binary executables
Authors: Yardimci Efe , Franz Michael
Published: June 2009

We have built a runtime compilation system that takes unmodified sequential binaries and improves their performance on off-the-shelf multiprocessors using dynamic vectorization and loop-level parallelization techniques. Our system, Azure, is purely software based and requires no specific hardware support for speculative thread execution, yet it is able to break even in most cases; that is, the achieved speedup exceeds the cost of runtime monitoring and compilation, often by significant amounts.

Key to this remarkable performance is an offline preprocessing step that extracts a
mostly correct
control flow graph (CFG) from the binary program ahead of time. This statically obtained CFG is incomplete in that it may be missing some edges corresponding to computed branches. We describe how such additional control flow edges are discovered and handled at runtime, so that an incomplete static analysis never leads to an incorrect optimization result.

The availability of a
mostly correct
CFG enables us to statically partition a binary executable into single-entry multiple-exit regions and to identify potential parallelization candidates ahead of execution. Program regions that are not candidates for parallelization can thereby be excluded completely from runtime monitoring and dynamic recompilation. Azure's extremely low overhead is a direct consequence of this design.
A theory of contracts for Web services
Authors: Castagna Giuseppe , Gesbert Nils , Padovani Luca
Published: June 2009

Contracts are behavioral descriptions of Web services. We devise a theory of contracts that formalizes the compatibility of a client with a service, and the safe replacement of a service with another service. The use of contracts statically ensures the successful completion of every possible interaction between compatible clients and services.

The technical device that underlies the theory is the
filter
, which is an explicit coercion preventing some possible behaviors of services and, in doing so, make services compatible with different usage scenarios. We show that filters can be seen as proofs of a sound and complete subcontracting deduction system which simultaneously refines and extends Hennessy's classical axiomatization of the must testing preorder. The relation is decidable, and the decision algorithm is obtained via a cut-elimination process that proves the coherence of subcontracting as a logical system.

Despite the richness of the technical development, the resulting approach is based on simple ideas and basic intuitions. Remarkably, its application is mostly independent of the language used to program the services or the clients. We outline the practical aspects of our theory by studying two different concrete syntaxes for contracts and applying each of them to Web services languages. We also explore implementation issues of filters and discuss the perspectives of future research this work opens.
IRLbot
Authors: Lee Hsin-Tsang , Leonard Derek , Wang Xiaoming , Loguinov Dmitri
Published: June 2009

This article shares our experience in designing a Web crawler that can download billions of pages using a single-server implementation and models its performance. We first show that current crawling algorithms cannot effectively cope with the sheer volume of URLs generated in large crawls, highly branching spam, legitimate multimillion-page blog sites, and infinite loops created by server-side scripts. We then offer a set of techniques for dealing with these issues and test their performance in an implementation we call IRLbot. In our recent experiment that lasted 41 days, IRLbot running on a single server successfully crawled 6.3 billion valid HTML pages (7.6 billion connection requests) and sustained an average download rate of 319 mb/s (1,789 pages/s). Unlike our prior experiments with algorithms proposed in related work, this version of IRLbot did not experience any bottlenecks and successfully handled content from over 117 million hosts, parsed out 394 billion links, and discovered a subset of the Web graph with 41 billion unique nodes.
Cookies
Authors: Tappenden Andrew F. , Miller James
Published: June 2009

The results of an extensive investigation of cookie deployment amongst 100,000 Internet sites are presented. Cookie deployment is found to be approaching universal levels and hence there exists an associated need for relevant Web and software engineering processes, specifically testing strategies which actively consider cookies. The semi-automated investigation demonstrates that over two-thirds of the sites studied deploy cookies. The investigation specifically examines the use of first-party, third-party, sessional, and persistent cookies within Web-based applications, identifying the presence of a P3P policy and dynamic Web technologies as major predictors of cookie usage. The results are juxtaposed with the lack of testing strategies present in the literature. A number of real-world examples, including two case studies are presented, further accentuating the need for comprehensive testing strategies for Web-based applications. The use of antirandom test case generation is explored with respect to the testing issues discussed. Finally, a number of seeding vectors are presented, providing a basis for testing cookies within Web-based applications.
A framework for QoS-based Web service contracting
Authors: Comuzzi Marco , Pernici Barbara
Published: June 2009

The extensive adoption of Web service-based applications in dynamic business scenarios, such as on-demand computing or highly reconfigurable virtual enterprises, advocates for methods and tools for the management of Web service nonfunctional aspects, such as Quality of Service (QoS). Concerning contracts on Web service QoS, the literature has mostly focused on the contract definition and on mechanisms for contract enactment, such as the monitoring of the satisfaction of negotiated QoS guarantees. In this context, this article proposes a framework for the automation of the Web service contract specification and establishment. An extensible model for defining both domain-dependent and domain-independent Web service QoS dimensions and a method for the automation of the contract establishment phase are proposed. We describe a matchmaking algorithm for the ranking of functionally equivalent services, which orders services on the basis of their ability to fulfill the service requestor requirements, while maintaining the price below a specified budget. We also provide an algorithm for the configuration of the negotiable part of the QoS Service-Level Agreement (SLA), which is used to configure the agreement with the top-ranked service identified in the matchmaking phase. Experimental results show that, in a utility theory perspective, the contract establishment phase leads to efficient outcomes. We envision two advanced application scenarios for the Web service contracting framework proposed in this article. First, it can be used to enhance Web services self-healing properties in reaction to QoS-related service failures; second, it can be exploited in process optimization for the online reconfiguration of candidate Web services QoS SLAs.
Unified publication and discovery of semantic Web services
Authors: Pilioura Thomi , Tsalgatidou Aphrodite
Published: June 2009

The challenge of publishing and discovering Web services has recently received lots of attention. Various solutions to this problem have been proposed which, apart from their offered advantages, suffer the following disadvantages: (i) most of them are syntactic-based, leading to poor precision and recall, (ii) they are not scalable to large numbers of services, and (iii) they are incompatible, thus yielding in cumbersome service publication and discovery. This article presents the principles, the functionality, and the design of PYRAMID-S which addresses these disadvantages by providing a scalable framework for unified publication and discovery of semantically enhanced services over heterogeneous registries. PYRAMID-S uses a hybrid peer-to-peer topology to organize Web service registries based on domains. In such a topology, each Registry retains its autonomy, meaning that it can use the publication and discovery mechanisms as well as the ontology of its choice. The viability of this approach is demonstrated through the implementation and experimental analysis of a prototype.
Player motivations
Authors: Bostan Barbaros
Published: June 2009

Although player motivation is one of the main concerns of computer gaming, research so far has been able to identify only a limited set of motives, which are not founded on formal theories of human motivation. Assuming that goal-directed behavior is triggered by the interaction between personal and environmental factors, this article aims to analyze a broader range of gaming motivations derived from basic human needs. The psychological needs investigated in this study are based on the psychogenic needs divided into six categories: materialism, power, affiliation, achievement, information, and sensual needs, defined by Murray [1938] in his extensive research. Since the present work defines motivation as a product of continuous interactions between players and the virtual world, each individual psychological need is briefly described in terms of the actions it provokes. In this context, this article is not concerned with why people play computer games but how they are motivated in the game.

Detailed analysis of the conceptual components of player motivation focuses on matching each psychological need to common gaming situations in computer role-playing games (RPGs). Since this game genre provides interactive virtual environments capable of offering experiences analogous to real life, it is highly relevant to motivational studies. The relationship between motivational factors and gaming situations is discussed with examples from a recently released RPG, which takes place in a fantasy world full of social issues and conflicts, where players usually find themselves in situations that require a choice between the lesser of two evils. It is expected that the variables defined in this study should facilitate the design of computer games that satisfy a broader range of player motivations by providing ways to investigate the relationship between psychological needs and the gaming environment, while bearing in mind the basic components of goal-directed behavior.
Enhancing the educational value of video games
Authors: Bellotti F. , Berta R. , Gloria A. De , Primavera L.
Published: June 2009

Lowering the barrier between education and real entertainment is an important challenge in order to better exploit the potential of computers and reach a demographic that is traditionally averse to learning. To this end, it is important to investigate how to exploit the appeal of video games (VGs) to also favor and induce learning via playing video games. Achieving this goal is not only a matter of content, since simply “superimposed” educational content risks being perceived as boring. Hence we believe that the game should feature mechanisms for acquiring knowledge and skill that are smoothly embedded in a meaningful, homogeneous, and compelling whole.

Thus, there is a need to compartmentalize components of a game engine so that it becomes easy and efficient to integrate the graphics/interface—which has already been done very well by state-of-the-art successful video games and the educational aspect which is typically poor in those same games. Hence we have defined a general set of mechanisms and modules that can be inserted in state-of-the-art VG environments and are aimed at promoting various kinds of knowledge and procedural skill acquisition.

In order to investigate and validate this concept, we have built an educational game,
SeaGame
, using a state-of-the-art commercial game development approach, and enriched the environment with instances of developed educational modules.

Analyzing user test results, we conclude that
SeaGame
is perceived quite similarly to commercial VGs, which suggests that the proposed mechanisms do not compromise the overall enjoyability of the game, which is key to attracting a wide demographic that is not currently involved in educational activities during their leisure time.

The results of this research can be generalized, since the standards of commercial games and the proposed educational enhancements can be instantiated in a variety of educational contexts and applied to different types of content.
The science and art of computer games development for undergraduate students
Authors: Taylor M. J. , Baskett M.
Published: June 2009

In this article we discuss an approach to teaching computer games development to higher education computing students that attempts to balance the artistic and scientific aspects of the computer game development process. The development of computer software has traditionally been viewed as a technical activity. However, unlike other existing types of computer software, a computer game is aimed at the general public (or specific segments of the general public such as teenagers), and needs to be designed in a different manner, with far more emphasis on interactivity, presentation, and ease-of-use than other existing types of computer software. This is necessary, since if a computer game does not appeal to the consumer, he or she will simply not purchase a copy of the game, or play the Internet-based game. Hence, students need to be taught how to incorporate both artistic and scientific aspects when designing a computer game.
Elaborating eight elements of fun
Authors: Jegers Kalle
Published: June 2009

This article presents the validation of the Pervasive GameFlow model (PGF), a model for analyzing player enjoyment in pervasive gaming. The model can be used as both a heuristic guideline for designers and as evaluation criteria in user-centered evaluation of pervasive games, but also as a framework for understanding player experiences in pervasive gaming on a more general level. The theoretical background and perspective on game design and the design- support approach that the PGF model represents are explained, and the concept of the magic circle is discussed. The eight elements of the PGF model (concentration, challenge, player skills, control, clear goals, feedback, immersion, and social interaction) were validated by evaluating a crossmedia game prototype (a subgenre of pervasive games) called
Furiae
. The comparative importance of the eight elements of the PGF model and their effects on the pervasive gaming experience was a focus of the evaluation, in which questionnaires (qualitative) and focus group interviews were used to capture how the players graded the importance of the eight elements in playing
Furiae
. The study revealed that seven of the eight elements seem to be of specific importance, as they scored relatively high in the validation. The top three elements according to the results are concentration (games should require concentration and the player should be able to concentrate on the game); challenge (games should be sufficiently challenging and match the player's skill level); and immersion (players should experience deep but effortless involvement in the game). Finally, implications for design are discussed in terms of how some of the most important elements present challenges and possibilities for crossmedia game development.
The gamer experience
Authors: Zaharias Panagiotis , Papargyris Anthony
Published: June 2009

Massively multiplayer online games (MMOGs) are persisted virtual worlds capable of supporting hundreds or thousands of gamers simultaneously. Although every MMOG environment has its own “culture,” gamers originate from different countries, speak different languages, and have different national cultural backgrounds. It is assumed that gamers' cultural diversity affects their online gaming experience and their perceptions of a game's usability; nevertheless knowledge is limited and relevant research is rare. This study aims for an empirical investigation between gamers' cultural dimensions and their perceptions of usability. A subjective measurement of usability is given in this study; usability is viewed in more holistic terms, beyond its functional dimensions, so as to capture social and affective dimensions as well, which are very important within the MMOG context. The findings of this exploratory study indicate that there are quantitative relationships between culture and the perception of usability of MMOGs. Such results have practical implications for the designers of MMOGs. A relevant discussion is also presented, along with future research dimensions.
Novel moving target search algorithms for computer gaming
Authors: Loh Peter K. K. , Prakash Edmond C.
Published: June 2009

In a computer game, equipping a bot with a suitable algorithm to locate a human player is difficult. Besides the unpredictable moves made by the player, an unexplored map region poses additional constraints such as new obstacles and pathways that the bot needs to discover quickly. The design criteria of such moving target search (MTS) algorithms would typically need to consider computation efficiency and storage requirements. That is, the bot must appear to be “smart” and “quick” in order to enhance the playability and challenge posed by the game. These criteria, however, pose conflicting requirements. In this article, we study and evaluate the performance and behavior of two novel MTS algorithms, Fuzzy MTS and Abstraction MTS, against existing MTS algorithms in randomly generated mazes of increasing size. Simulations reveal that Fuzzy MTS and Abstraction MTS exhibit competitive performance even with large problem spaces.
Data integration in mashups
Authors: Di Lorenzo Giusy , Hacid Hakim , Paik Hye-young , Benatallah Boualem
Published: June 2009

Mashup is a new application development approach that allows users to aggregate multiple services to create a service for a new purpose. Even if the Mashup approach opens new and broader opportunities for data/service consumers, the development process still requires the users to know not only how to write code using programming languages, but also how to use the different Web APIs from different services. In order to solve this problem, there is increasing effort put into developing tools which are designed to support users with little programming knowledge in Mashup applications development. The objective of this study is to analyze the richnesses and weaknesses of the Mashup tools with respect to the data integration aspect.
Distributed utility-based rate adaptation protocols for prioritized, quasi-elastic flows
Authors: Eswaran Sharanya , Johnson Matthew P. , Misra Archan , La Porta Thomas
Published: June 2009

This paper considers rate adaptation for streaming multimedia data in a wireless sensor network (WSN) consisting of multiple missions, where each mission subscribes to data streams from multiple sensors, and each sensor's data is utilized by multiple heterogenous missions. We specifically consider the application of the distributed network utility maximization (NUM) framework to a previously unconsidered scenario where the different missions have different priorities, as well as minimum utility demands. When all the utility demands are feasible, we first show that the addition of a penalty for failing to reach the minimum utility demand to the base NUM protocol leads to maximization of the global utility. The paper, however, principally focuses on those situations where the minimum demands cannot all be satisfied due to resource constraints. To address such practical scenarios, we present and evaluate a) a family of modified NUM-based protocols to determine the optimal satisfied set, when the missions have unique priority order, and b) heuristics for applying NUM, when multiple missions have the same priority.
Tradeoffs between jamming resilience and communication efficiency in key establishment
Authors: Slater David , Poovendran Radha , Tague Patrick , Matt Brian J.
Published: June 2009

We address the problem of allowing authorized users, who do not preshare a common key, to effectively exchange key establishment messages over an insecure channel in the presence of jamming and message insertion attacks. In this work, we jointly consider the security and efficiency of key exchange protocols, focusing on the interplay between message fragmentation, jamming resilience, and verification complexity for protocol optimization. Finally, we present three fragment verification schemes and demonstrate through analysis and simulation that in comparison with existing approaches, they can significantly decrease the amount of time required for key establishment without degrading the guaranteed level of security.
Voice and video capacity of a secure IEEE 802.11g wireless network
Authors: Mullins Barry E. , Seyba Jason R. , Raines Richard A. , Ramsey Benjamin W.P. , Williams Paul D.
Published: June 2009

This paper describes an empirical evaluation of the ability of an IEEE 802.11g network to transport audio and video as well as compare audio quality in the presence and absence of an access point within an office environment using standard off-the-shelf hardware and default device configurations. The impact of securing the audio stream with WPA (WiFi Protected Access) on the perceived quality is also examined. Following the ITU-T P.800 recommendation, thirty-six human subjects assess audio and video quality using a Mean Opinion Score (MOS) on a wireless multimedia system. Experimental data suggest that securing the voice traffic has no significant effect on the quality of the audio signal received. Furthermore, an 18.4% improvement in the perceived quality of the audio signal can be achieved by routing the audio and video traffic through an access point instead of allowing the audio and video traffic to flow directly between two arbitrary nodes within a wireless local area network. Furthermore, increasing the number of conversations reduces the perceived quality of the audio signal by 23.5% and the video signal by 16.8%. Disabling video increases the perceived audio quality by 38.9%. This paper shows that the usable capacity, based on signal quality, of a standard IEEE 802.11g wireless multimedia system deployed in an office environment is two audio-only conversations or one audio/one video connection on the wireless network.