Development of an atomic‐broadcast protocol using LOTOS

In this article we report on the development of a group‐communication service using the formal specification language LOTOS, and present our experience in using publicly available tools for this purpose. The service implements atomic broadcast through a Two‐Phase‐Commit protocol, providing at‐least‐once delivery semantics and with no restriction on message delivery order. First we wrote an informal specification describing the desired properties from the service, the interfaces with the underlying network layer and the upper user layer, and the protocol to be used by the service. Then we developed the formal specification of the protocol in LOTOS. After validating the formal specification and thus having a certain confidence in its adequacy with respect to the informal specification, we derived test cases from the formal specification and implemented the service using the Concert/C distributed programming language. While testing the implementation, we found that most errors were related to unspecified features or bugs in the execution environment. From this experience, we draw our conclusions on the usefulness of software development based on formal techniques. Copyright © 1999 John Wiley & Sons, Ltd.     

Application‐specific thread schedulers for distributed applications

This paper describes our work to improve the performance of distributed applications. We aim at certain application characteristics such as balancing load, allowing separately written applications to work better together, allowing a distributed application to adapt its behavior in more flexible ways, and so on. Our approach is to write application‐specific schedulers, which can access the global state of the application in making scheduling decisions. To achieve this goal, we extended our earlier work on CATAPULTS ( C reating A nd T esting AP plication‐specific U ser L evel T hread S chedulers), a domain‐specific language for creating and testing application‐specific user‐level thread schedulers, to distributed applications by adding ‘master schedulers’ for dealing with the distributed parts of applications. This paper presents our design of, experimentation with, and implementation of distributed CATAPULTS. This paper presents several realistic examples to measure the feasibility of this approach, specifically: a website application, an embedded application, and load balancing. Each example has a scheduling goal for which we developed a customized scheduler. We measured the performance with and without the customized scheduler. The customized scheduler for each example was fairly straightforward to develop and each achieved its scheduling goal. Copyright © 2011 John Wiley & Sons, Ltd.     

Low‐level PGAS computing on many‐core processors with TSHMEM

Diminishing returns from increased clock frequencies and instruction‐level parallelism have forced computer architects to adopt architectures that exploit wider parallelism through multiple processor cores. While emerging many‐core architectures have progressed at a remarkable rate, concerns arise regarding the performance and productivity of numerous parallel‐programming tools for application development. Development of parallel applications on many‐core processors often requires developers to familiarize themselves with unique characteristics of a target platform while attempting to maximize performance and maintain correctness of their applications. The family of partitioned global address space (PGAS) programming models comprises the current state of the art in balancing performance and programmability. One such PGAS approach is SHMEM, a lightweight, shared‐memory programming library that has demonstrated high performance and productivity potential for parallel‐computing systems with distributed‐memory architectures. In the paper, we present research, design, and analysis of a new SHMEM infrastructure specifically crafted for low‐level PGAS on modern and emerging many‐core processors featuring dozens of cores and more. Our approach (with a new library known as TSHMEM) is investigated and evaluated atop two generations of Tilera architectures, which are among the most sophisticated and scalable many‐core processors to date, and is intended to enable similar libraries atop other architectures now emerging. In developing TSHMEM, we explore design decisions and their impact on parallel performance for the Tilera TILE‐Gx and TILEPro many‐core architectures, and then evaluate the designs and algorithms within TSHMEM through microbenchmarking and applications studies with other communication libraries. Our results with barrier primitives provided by the Tilera libraries show dissimilar performance between the TILE‐Gx and TILEPro; therefore, TSHMEM's barrier design takes an alternative approach and leverages the on‐chip mesh network to provide consistent low‐latency performance. In addition, our experiments with TSHMEM show that naive collective algorithms consistently outperformed linear distributed collective algorithms when executed in an SMP‐centric environment. In leveraging these insights for the design of TSHMEM, our approach outperforms the OpenSHMEM reference implementation, achieves similar to positive performance over OpenMP and OSHMPI atop MPICH, and supports similar libraries in delivering high‐performance parallel computing to emerging many‐core systems. Copyright © 2015 John Wiley & Sons, Ltd.     

Towards generic representation of web applications: solutions and trade‐offs

Server pages (also called dynamic pages) render a generic web page into many similar ones. The technique is commonly used for implementing web application user interfaces (UIs). Yet our previous study found a high rate of repetitions (also called ‘clones’) in web applications, particularly in UIs. The finding raised the question as to why such repetitions had not been averted with the use of server pages. For an answer, we conducted an experiment using PHP server pages to explore how far server pages can be pushed to achieve generic web applications. Our initial findings suggested that generic representation obtained using server pages sometimes compromises certain important system qualities such as run‐time performance. It may also complicate the use of WYSIWYG editors. We have analysed the nature of these trade‐offs, and now propose a mixed‐strategy approach to obtain optimum generic representation of web applications without unnecessary compromise to critical system qualities and user experience. The mixed‐strategy approach applies the generative technique of XVCL to achieve genericity at the meta‐level representation of a web application, leaving repetitions to the actual web application. Our experiments show that the mixed‐strategy approach can achieve a good level of genericity without conflicting with other system qualities. Our findings should open the way for others to better‐informed decisions regarding generic design solutions, which should in turn lead to simpler, more maintainable and more reusable web applications. Copyright © 2008 John Wiley & Sons, Ltd.     

As‐Killing‐As‐Possible Vector Fields for Planar Deformation

Cartoon animation, image warping, and several other tasks in two‐dimensional computer graphics reduce to the formulation of a reasonable model for planar deformation. A deformation is a map from a given shape to a new one, and its quality is determined by the type of distortion it introduces. In many applications, a desirable map is as isometric as possible. Finding such deformations, however, is a nonlinear problem, and most of the existing solutions approach it by minimizing a nonlinear energy. Such methods are not guaranteed to converge to a global optimum and often suffer from robustness issues. We propose a new approach based on approximate Killing vector fields (AKVFs), first introduced in shape processing. AKVFs generate near‐isometric deformations, which can be motivated as direction fields minimizing an “as‐rigid‐as‐possible” (ARAP) energy to first order. We first solve for an AKVF on the domain given user constraints via a linear optimization problem and then use this AKVF as the initial velocity field of the deformation. In this way, we transfer the inherent nonlinearity of the deformation problem to finding trajectories for each point of the domain having the given initial velocities. We show that a specific class of trajectories — the set of logarithmic spirals — is especially suited for this task both in practice and through its relationship to linear holomorphic vector fields. We demonstrate the effectiveness of our method for planar deformation by comparing it with existing state‐of‐the‐art deformation methods.     

H∞ finite‐horizon filtering for complex networks with state saturations: The weighted try‐once‐discard protocol

This paper addresses the finite‐horizon H_∞ filtering problem for a kind of discrete state‐saturated time‐varying complex networks subjected to the weighted try‐once‐discard (WTOD) protocol. Under the WTOD protocol, only the measurement signal from one sensor node is allowed to be transmitted to the filter at each time point, where such a node is selected based on a certain quadratic selection principle. The main purpose of this paper is to design an H_∞ filter that guarantees the disturbance attenuation level on a given finite time‐horizon for the underlying complex network subject to both state saturations and WTOD protocols. By using the convex hull approach, sufficient conditions are first obtained to ensure the existence for the desired filter to achieve the H_∞ performance specification by means of a few recursive matrix inequalities. Then, based on the obtained results, the filter parameters are designed, which cope effectively with both state saturations and communication protocols. Finally, a numerical simulation is employed to demonstrate the validity of the developed filter algorithm.     

Experiences developing architectures for realizing thin‐client diagram editing tools

Diagram‐centric applications such as software design tools, project planning tools and business process modelling tools are usually ‘thick‐client’ applications running as stand‐alone desktop applications. There are several advantages to providing such design tools as Web‐based or even PDA‐ and mobile‐phone‐based applications. These include ease of access and upgrade, provision of collaborative work support and Web‐based integration with other applications. However, building such thin‐client diagram editing tools is very challenging. We have developed several thin‐client diagram editing applications realized as a set of plug‐in extensions to a meta‐tool for visual design environment development. In this paper, we discuss key user interaction and software architecture issues, illustrate examples of interacting with our thin‐client diagram editing tools, describe our design and implementation approaches, and present the results of several different evaluations of the resultant applications. Our experiences will be useful for those interested in developing their own thin‐client diagram editing architectures and applications. Copyright © 2007 John Wiley & Sons, Ltd.     

Using meta‐modeling in design and implementation of component‐based systems: the SOFA case study

To allow efficient and user‐friendly development of a component‐based application, component systems have to provide a rather complex development infrastructure, including a tool for component composition, component repository, and a run‐time infrastructure. In this paper, we present and evaluate benefits of using meta‐modeling during the process of defining a component system and also during creation of the development and run‐time infrastructures. Most of the presented arguments are based on a broad practical experience with designing the component systems SOFA and SOFA 2; the former designed in a classical ad hoc ‘manual’ way, whereas the latter with the help of meta‐modeling. Copyright © 2010 John Wiley & Sons, Ltd.     

Visualizing Waypoints‐Constrained Origin‐Destination Patterns for Massive Transportation Data

Origin‐destination (OD) pattern is a highly useful means for transportation research since it summarizes urban dynamics and human mobility. However, existing visual analytics are insufficient for certain OD analytical tasks needed in transport research. For example, transport researchers are interested in path‐related movements across congested roads, besides global patterns over the entire domain. Driven by this need, we propose waypoints‐constrained OD visual analytics, a new approach for exploring path‐related OD patterns in an urban transportation network. First, we use hashing‐based query to support interactive filtering of trajectories through user‐specified waypoints. Second, we elaborate a set of design principles and rules, and derive a novel unified visual representation called the waypoints‐constrained OD view by carefully considering the OD flow presentation, the temporal variation, spatial layout and user interaction. Finally, we demonstrate the effectiveness of our interface with two case studies and expert interviews with five transportation experts.     

A compact dual‐band zeroth‐order resonator antenna loaded with meander line inductor

A novel zeroth‐order resonator (ZOR) meta‐material (MTM) antenna with dual‐band is suggested using compound right/left handed transmission line as MTM. In this article, suggested antenna consists of patch through series gap, two meander line inductors, and two circular stubs. The MTM antenna is compact in size which shows dual‐band properties with first band centered at 2.47 GHz (2.05‐2.89 GHz) and second band is centered at 5.9 GHz (3.70‐8.10 GHz) with impedance bandwidth of (S₁₁ < ? 10 dB) 34.69% and 72.45%, respectively. At ZOR mode (2.35 GHz), the suggested antenna has overall dimension of 0.197λ_o × 0.07λ_o × 0.011λ_o with gain of 1.65 dB for ZOR band and 3.35 dB for first positive order resonator band which covers the applications like Bluetooth (2.4 GHZ), TV/Radio/Data (3.700‐6.425 GHz), WLAN (5‐5.16 GHz), C band frequencies (5.15‐5.35, 5.47‐5.725, or 5.725‐5.875 GHz) and satellite communication (7.25‐7.9 GHz). The radiation patterns of suggested structure are steady during the operating band for which sample antenna has been fabricated and confirmed experimentally. It exhibits novel omnidirectional radiation characteristics in phi = 0° plane with lower cross‐polarization values.     

Circularly polarized quad‐band monopole antenna of wireless communication system

In this article, multiband monopole antenna has been designed for the applications of wireless communication systems. The antenna is composed of I‐shaped strips which are placed in such a way that the each of the resonating strips produced distinct frequency bands. The optimum dimension of the proposed antenna is printed on dielectric substrates of FR4 epoxy having dimensions of 0.3λ₀ × 0.21λ₀ × 0.009λ₀. The antenna has been fabricated and measured for evidence. The measured results are verified with simulated results. The comparison of simulated and measured S₁₁ parameter, radiation pattern, peak gains, and circular polarization are described in the section of experimental results. The measured result shows that the antenna may cover the frequency band of Digital Cellular System, Personal Communications Service, Long Term Evolution‐4G, Bluetooth, Worldwide Interoperability Microwave Access, Wireless Local Area Network, 802.11j (WLAN‐Public Safety), and X‐band (Satellite Communication‐downlink).     

Dynamics and control in component‐based agent models

Dynamics are an important aspect of agent models. Control of dynamics requires specific methods of specification that have their own specific semantics. This paper addresses specification and semantics of dynamics and control in component‐based agent models. Specification is based on a dedicated formal design specification language for agent models. Semantics of the dynamics are defined using temporal traces with composite states. It is shown in what manner control aspects can be specified, and what their semantics is in terms of the temporal traces. An agent model for controlled diagnostic reasoning processes is used to illustrate the approach. © 2002 Wiley Periodicals, Inc.     

On open‐set lattices and some of their applications in semantics

In this article, we present the theory of Kripke semantics, along with the mathematical framework and applications of Kripke semantics. We take the Kripke‐Sato approach to define the knowledge operator in relation to Hintikka's possible worlds model, which is an application of the semantics of intuitionistic logic and modal logic. The applications are interesting from the viewpoint of agent interactives and process interaction. We propose (i) an application of possible worlds semantics, which enables the evaluation of the truth value of a conditional sentence without explicitly defining the operator “→” (implication), through clustering on the space of events (worlds) using the notion of neighborhood; and (ii) a semantical approach to treat discrete dynamic process using Kripke‐Beth semantics. Starting from the topological approach, we define the measure‐theoretical machinery, in particular, we adopt the methods developed in stochastic process—mainly the martingale—to our semantics; this involves some Boolean algebraic (BA) manipulations. The clustering on the space of events (worlds), using the notion of neighborhood, enables us to define an accessibility relation that is necessary for the evaluation of the conditional sentence. Our approach is by taking the neighborhood as an open set and looking at topological properties using metric space, in particular, the so‐called ε‐ball; then, we can perform the implication by computing Euclidean distance, whenever we introduce a certain enumerative scheme to transform the semantic objects into mathematical objects. Thus, this method provides an approach to quantify semantic notions. Combining with modal operators K_i operating on E set, it provides a more‐computable way to recognize the “indistinguishability” in some applications, e.g., electronic catalogue. Because semantics used in this context is a local matter, we also propose the application of sheaf theory for passing local information to global information. By looking at Kripke interpretation as a function with values in an open‐set lattice ??_U, which is formed by stepwise verification process, we obtain a topological space structure. Now, using the measure‐theoretical approach by taking the Borel set and Borel function in defining measurable functions, this can be extended to treat the dynamical aspect of processes; from the stochastic process, considered as a family of random variables over a measure space (the probability space triple), we draw two strong parallels between Kripke semantics and stochastic process (mainly martingales): first, the strong affinity of Kripke‐Beth path semantics and time path of the process; and second, the treatment of time as parametrization to the dynamic process using the technique of filtration, adapted process, and progressive process. The technique provides very effective manipulation of BA in the form of random variables and σ‐subalgebra under the cover of measurable functions. This enables us to adopt the computational algorithms obtained for stochastic processes to path semantics. Besides, using the technique of measurable functions, we indeed obtain an intrinsic way to introduce the notion of time sequence. © 2003 Wiley Periodicals, Inc.     

A quality‐of‐service‐based framework for creating distributed heterogeneous software components

Component‐based software development offers a promising solution for taming the complexity found in today's distributed applications. Today's and future distributed software systems will certainly require combining heterogeneous software components that are geographically dispersed. For the successful deployment of such a software system, it is necessary that its realization, based on assembling heterogeneous components, not only meets the functional requirements, but also satisfies the non‐functional criteria such as the desired quality of service (QoS). In this paper, a framework based on the notions of a meta‐component model, a generative domain model and QoS parameters is described. A formal specification based on two‐level grammar is used to represent these notions in a tightly integrated way so that QoS becomes a part of the generative domain model. A simple case study is described in the context of this framework. Copyright © 2002 John Wiley & Sons, Ltd.     

Structured H∞‐control of infinite‐dimensional systems

We develop a novel frequency‐based H_∞‐control method for a large class of infinite‐dimensional linear time‐invariant systems in transfer function form. A major benefit of our approach is that reduction or identification techniques are not needed, which avoids typical distortions. Our method allows to exploit both state‐space or transfer function models and input/output frequency response data when only such are available. We aim for the design of practically useful H_∞‐controllers of any convenient structure and size. We use a nonsmooth trust‐region bundle method to compute arbitrarily structured locally optimal H_∞‐controllers for a frequency‐sampled approximation of the underlying infinite‐dimensional H_∞‐problem in such a way that (i) exponential stability in closed loop is guaranteed and that (ii) the optimal H_∞‐value of the approximation differs from the true infinite‐dimensional value only by a prior user‐specified tolerance. We demonstrate the versatility and practicality of our method on a variety of infinite‐dimensional H_∞‐synthesis problems, including distributed and boundary control of partial differential equations, control of dead‐time and delay systems, and using a rich testing set.     

COIVA: context‐aware and ontology‐powered information visualization architecture

This paper exploits semantics to apply context in run‐time adaptation, particularly for services in a user‐centered smart environment. Context‐sensitive services are usually focused on their own information without interoperation pretensions. It is necessary to enable common context models and systems in order to make context‐aware applications interoperable. Moreover, context management systems need to implement mechanisms to support the dynamic behavior of the users and their surroundings, including techniques to adapt the model to their future needs, to maintain the context information at run‐time and to be interoperable with external context models. By adapting web semantic technologies we can enable smarter and more proactive operation of context management systems. Copyright © 2010 John Wiley & Sons, Ltd.     

Semi‐automatic grammar recovery

We propose an approach to the construction of grammars for existing languages. The main characteristic of the approach is that the grammars are not constructed from scratch but they are rather recovered by extracting them from language references, compilers and other artifacts. We provide a structured process to recover grammars including the adaptation of raw extracted grammars and the derivation of parsers. The process is applicable to possibly all existing languages for which business critical applications exist. We illustrate the approach with a non‐trivial case study. Using our process and some basic tools, we constructed in a few weeks a complete and correct VS COBOL II grammar specification for IBM mainframes. In addition, we constructed a parser for VS COBOL II, and were the first to publish a (Web‐enabled) grammar specification so that others can use this result to construct their own grammar‐based tools for VS COBOL II or derivatives. Copyright © 2001 John Wiley & Sons, Ltd.     

Example‐Based Retargeting of Human Motion to Arbitrary Mesh Models

We present a novel method for retargeting human motion to arbitrary 3D mesh models with as little user interaction as possible. Traditional motion‐retargeting systems try to preserve the original motion, while satisfying several motion constraints. Our method uses a few pose‐to‐pose examples provided by the user to extract the desired semantics behind the retargeting process while not limiting the transfer to being only literal. Thus, mesh models with different structures and/or motion semantics from humanoid skeletons become possible targets. Also considering the fact that most publicly available mesh models lack additional structure (e.g. skeleton), our method dispenses with the need for such a structure by means of a built‐in surface‐based deformation system. As deformation for animation purposes may require non‐rigid behaviour, we augment existing rigid deformation approaches to provide volume‐preserving and squash‐and‐stretch deformations. We demonstrate our approach on well‐known mesh models along with several publicly available motion‐capture sequences.     

Timing analysis of scenario‐based specifications using linear programming

Scenario‐based specifications (SBSs), such as UML interaction models, offer an intuitive and visual way of describing design requirements, and are playing an increasingly important role in the design of software systems. This paper presents an approach to timing analysis of SBSs expressed by UML interaction models. The approach considers more general and expressive timing constraints in UML sequence diagrams (SDs), and gives a solution to the reachability analysis, constraint conformance analysis and bounded delay analysis problems, which reduces these problems into linear programs. With the synchronous interpretation of the SD compositions, the timing analysis algorithms in the approach form a decision procedure for a class of SBSs where any loop in any path is time‐independent of the other parts in the path. These algorithms are also a semi‐decision procedure for general SBSs with both the synchronous and asynchronous composition semantics. The approach also supports bounded timing analysis of SBSs, which investigates all the paths in the bound limit one by one, and performs the timing analysis for each finite path by linear programming. A tool prototype has been developed to support this approach. Copyright © 2010 John Wiley & Sons, Ltd.     

Content‐Aware Automatic Photo Enhancement

Automatic photo enhancement is one of the long‐standing goals in image processing and computational photography. While a variety of methods have been proposed for manipulating tone and colour, most automatic methods used in practice, operate on the entire image without attempting to take the content of the image into account. In this paper, we present a new framework for automatic photo enhancement that attempts to take local and global image semantics into account. Specifically, our content‐aware scheme attempts to detect and enhance the appearance of human faces, blue skies with or without clouds and underexposed salient regions. A user study was conducted that demonstrates the effectiveness of the proposed approach compared to existing auto‐enhancement tools.